Effect of solvent polarity in formation of perfectly ordered CMK-3 and CMK-5 carbon replicas by precipitation polycondensation of furfuryl alcohol

Two twin series of carbon replicas were synthesized by the acid-catalyzed precipitation polycondensation of various amounts of furfuryl alcohol in SBA-15 suspensions using water and toluene as reaction media. The textural and structural parameters, as well as the morphology of the polymer/silica carbonizates and corresponding replicas, were investigated comprehensively.

Microporous and Mesoporous Materials 329 (2022) 111542 Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso Effect of solvent polarity in formation of perfectly ordered CMK-3 and CMK-5 carbon replicas by precipitation polycondensation of furfuryl alcohol ´ ski c, Mariusz Wądrzyk a, b, Marek Lewandowski a, b, Piotr Łątka c, Rafał Janus a, b, *, Piotr Natkan Piotr Ku´strowski c a AGH University of Science and Technology, Faculty of Energy and Fuels, Al A Mickiewicza 30, 30-059, Krak´ ow, Poland AGH University of Science and Technology, AGH Centre of Energy, Ul Czarnowiejska 36, 30-054, Krak´ ow, Poland c Jagiellonian University, Faculty of Chemistry, Ul Gronostajowa 2, 30-387, Krak´ ow, Poland b A R T I C L E I N F O A B S T R A C T Keywords: CMK-3 CMK-5 Carbon replica Poly(furfuryl alcohol) Nanocasting SBA-15 Two twin series of carbon replicas were synthesized by the acid-catalyzed precipitation polycondensation of various amounts of furfuryl alcohol in SBA-15 suspensions using water and toluene as reaction media The textural and structural parameters, as well as the morphology of the polymer/silica carbonizates and corre­ sponding replicas, were investigated comprehensively It was found that the polarity of the reaction medium plays an essential role in the scenario of the deposition of poly(furfuryl alcohol) (PFA) onto the surface of the silica matrix Namely, the water-based environment results in propagating PFA chains radially from the pore centres to the wall thereof, while in the case of toluene its growth progresses in the reverse direction The spectroscopic studies disclosed that this is due to the competitive adsorption of monomer and solvent on the superficial silica silanol groups In the case of the water-furfuryl alcohol system, H2O is adsorbed preferentially, hindering the formation of a homogenous polymer layer, thus precluding the formation of a hollow-type replica Contrarily, for the toluene-furfuryl alcohol mixture, the monomer adsorption is favored Furthermore, the forming polymer anchors to the silica surface covalently and clads it evenly, therefore facilitating the formation of a high-quality CMK-5 structure Introduction esterification and transesterification, oxidative degradation) [10, 12–18], adsorptive hydrogen storage [9], purification (e.g removal of volatile organic compounds, NOx, and sulfur-containing compounds, as well as CO2 capturing) [19–23], electrochemistry (as electrical double layer (super)capacitors) [6,24–26], and medical purposes (mainly as intracorporeal drug delivery carriers) [7,8,27–29] Moreover, carbon replicas are excellent model materials for a theoretical study of diffusion and adsorption phenomena in porous solids [30–33], as well as XRD patterns simulation/prediction [34] Another interesting application involves their use in the synthesis of mesoporous inorganic materials (commonly metal oxides) featuring the structure of original silica matrices (secondary replication of carbon structures) [35,36] Attempts were also made to synthesize metal oxides exactly imitating the struc­ tures of replicas [37] Furthermore, it is well-documented that carbon replication may be an ingenious tool for investigation of structures of porous materials [1,38–42,47] Recently, we reported on the elucidation Ordered Mesoporous Carbons (OMCs), also called carbon replicas, pose a class of nanoporous materials offering unique structural and surface beneficial properties They show such remarkable properties as a long-range mesoscopic ordering, excellent homogeneity of pore shape and size, highly developed specific surface area (up to ca 2500 m2 g− 1), and large total pore volume (even 2.5 cm3 g− 1) [1–4] However, the most desirable feature of OMCs is the opportunity of precise control of their structure at the synthesis stage and ease of surface modification [5–11] With this, it is not surprising that in the last two decades carbon replicas have attracted extensive interest in the scientific community, especially for these purposes in which a well-defined porosity with a long-range ordering is required The favorable properties of OMCs resulted in their successful applications as functional materials in a va­ riety of fields, including catalysis (e.g hydrocarbons dehydrogenation, * Corresponding author AGH University of Science and Technology, Faculty of Energy and Fuels, Al A Mickiewicza 30, 30-059, Krak´ ow, Poland E-mail address: rjanus@agh.edu.pl (R Janus) https://doi.org/10.1016/j.micromeso.2021.111542 Received 20 September 2021; Received in revised form 26 October 2021; Accepted 29 October 2021 Available online November 2021 1387-1811/© 2021 The Authors Published by Elsevier Inc This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 of the mechanism of pseudomorphic transformation (PT) of porous sil­ icas by non-direct investigation of the daughter carbon structures of the SBA-15 upon partial PT into MCM-41 [43] The pioneering synthesis of carbon replicas has been published in 1999 by the group of researchers from the Korea Advanced Institute of Science and Technology (KAIST) [2] The proposed synthetic route al­ lows the preparation of negative carbon structures (inverse replicas) cast from porous silica materials (matrices) based on a so-called hard tem­ plating strategy It consists in filling the pore system (either partial or complete) of a mineral matrix with a proper carbon precursor followed by carbonization of the composite and removal of the inorganic template by etching with alkali or hydrofluoric acid The first replica, called CMK-1 (Carbon Mesostructured by KAIST) was synthesized by impreg­ nation of MCM-48 silica with an acidified sucrose solution as a carbon source [2] Inspired by Ryoo, other researchers put efforts to synthesize a family of replicas employing silicas with different pore system ar­ rangements and a variety of carbon precursors used in various amounts The ultimate solids featured symmetry elements identical to the matrices, although they were exact structural negatives thereof Furthermore, the partial pore filling of the silica matrix with a carbon precursor may lead (but needs not) to the formation of open-work hol­ low-type frameworks, whereas total filling results in obtaining rod-type replicas The materials were marked with the common acronym CMK-n, where n = 1–9 and differs depending on the matrix used and refers to the ultimate carbon framework type [3] The efficiency of carbon precursor deposition in the pores of silica plays a crucial role in the quality of the resulting final replica (i.e the fidelity of matrix structure replication) Besides the aforementioned impregnation, early methods of carbon precursor incorporation included chemical vapor deposition (CVD) However, this approach requires the use of an advanced apparatus and is time- and energyconsuming Moreover, prior to the deposition of carbon precursor, the matrix surface has to be properly modified (generation of active centres catalyzing the polymerization of carbon precursor) [44–46] Obviously, such a sophisticated synthesis path precludes the possibility of utilizing carbon replicas on a technical scale Therefore, the reported application tests, although gave very promising results, did not pass beyond the laboratory scale, and attempts to synthesize high-quality hollow-type structures (in fact, more challenging than the rod-type ones) have been scarcely reported [3,18,47,48] In our former study, we put efforts to develop a simplified route for the synthesis of carbon replicas [12,49] The novelty of our approach consisted on employing the precipitation polymerization of carbon precursor’s monomer onto the silica matrix walls in liquid media Based on this strategy, we successfully synthesized the CMK-3 replica by nanocasting of the SBA-15 silica by the acid-catalyzed polycondensation of furfuryl alcohol in an aqueous suspension of the rigid template This procedure led to the complete filling of the channel system of SiO2 and allowed to shorten the synthesis time while using a green reaction me­ dium Moreover, we managed to eliminate the step of preliminary modification of silica These encouraging findings gave rise to undertaking attempts to employ the same procedure to obtain the corresponding hollow-type CMK-5 replica Unexpectedly, the intended material has finally not been obtained, although another interesting structure with bimodal meso­ porosity was created (the so-called pseudo-CMK-3) [15,50] It was found that the chemical nature of the medium used for the decoration of silica with a polymer governs the manner of the carbon source deposition (the homogeneous coating of the silica walls with polymer performed in the water environment is not feasible) Furthermore, we hypothesized that the solvent’s polarity and its possible interaction with the superficial SBA-15 silanols may affect the mechanism of PFA deposition (e.g due to the competitive solvent-monomer adsorption hindering the homoge­ neous distribution of carbon precursor) This may influence (either deteriorate or improve) the structural quality of the ultimate OMC Noteworthy, since our first report on PFA deposition in an aqueous medium [12], there is a lack of research on the use of other media in the literature We have found this issue worth investigating as it is plausible that the deposition of the carbon precursor in liquid media is more ho­ mogeneous than that of impregnation, being the most common pro­ cedure In fact, the impregnation may be influenced by the local fluctuations in the monomer concentration caused by the evaporation of the solvent Contrarily, the polymer precipitation in liquid media is a self-regulating process driven by the affinity of the monomer to the silica’s surface In this work we elucidate the role of the polarity of the medium used for the precipitation of poly(furfuryl alcohol) onto SBA-15 silica matrix walls on the mechanism of its deposition This was feasible by the investigation on textural and structural characteristics (N2 adsorption and low-angle XRD, respectively), morphology (TEM), and spectro­ scopic study (FT-IR and XPS), which were carried out for two twin series of replicas synthesized in water and toluene It was found that using polar solvent results in propagating polymer chains radially from the bulk monomer solution to the silica pore wall, while in the case of nonpolar medium their growth progresses in the reverse direction As a result, the polar medium precludes the formation of a hollow-type replica, whereas the nonpolar solvent facilitates the formation of an excellent CMK-5 structure This finding may be a cornerstone to the development of a simple and versatile method for the synthesis of other carbon replicas Experimental section 2.1 Synthesis All chemicals were commercially available and used without further purification Tetraethyl orthosilicate (TEOS, 98.0%) was purchased from Acros Organics, poly(ethylene oxide)-block-poly(propylene oxide)block-poly(ethylene oxide) triblock copolymer (Pluronic P123), furfuryl alcohol (FA, 98%), hydrofluoric acid (40–45%), potassium bromide (≥99.0%), and isopropanol (≥99.5%) were supplied by Sigma-Aldrich, whereas hydrochloric acid (35–38%, pure p.a.), tartaric acid (TA, pure p.a.), toluene (pure p.a.), and sodium sulphate anhydrous (99.0%) were purchased from Avantor Performance Materials Poland 2.1.1 SBA-15 SBA-15 silica matrix was synthesized under acidic conditions at a molar gel composition of 1.00 TEOS: 0.02 Pluronic P123: 2.94 HCl: 116.46 H2O according to the procedure reported elsewhere after fivefold scale enlargement [12] In brief, an amount of 85.00 g of TEOS (cooled to ◦ C) was slowly instilled (2 drops s− 1) and hydrolyzed at 35 ◦ C for 22 h in a mixture containing 40.00 g of Pluronic P123 dissolved before in 300.00 g of distilled water mixed with 600.00 g of M HCl in a 2000 cm3 round-bottom flask placed in a silicone oil bath and equipped with a reflux condenser Subsequently, the milky reaction mixture was trans­ ferred to a laboratory dryer and kept statically at 100 ◦ C for 72 h (pre­ cipitate aging step) Then, the white product was recovered by filtration, washed with 500 cm3 of distilled water, and dried at 60 ◦ C for 48 h Finally, the structure-directing agent was removed by calcination of the silica/P123 composite in a muffle furnace under an air atmosphere at 550 ◦ C for 10 h at a heating rate of β = ◦ C min− The ultimate material was marked as SBA-15 A small portion of as-made SBA-15 was calcined using the identical thermal regime as for carbonization (850 ◦ C for h, β = ◦ C min− 1) This sample was labelled as SBA-15@850 2.1.2 Carbon replicas Two twin series of carbon replicas were cast from SBA-15 by the acidcatalyzed precipitation polycondensation of various amounts of FA in suspensions of the matrix, according to the modified procedure reported in our former works [12,15,49] The series differed in the liquid media used for the incorporation of PFA into SBA-15 pores These media were selected in such a way to be significantly different in polarity and to be R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 miscible with the monomer For this purpose, water (dipole moment μ = 1.85 D) and toluene (μ = 0.36 D) (W- and T-series, respectively) were chosen The use of tartaric acid as a catalyst with lower acid strength than in our earlier reports (hydrochloric acid) (for HCl pKa = − 6.3, while for TA pKa1 = 2.98, and pKa2 = 4.34; each value given for water solution) enabled the slower deposition of the polymer in the pores of SBA-15 This prevented clogging the pores by the rapid growth of the polymer plugs near the pore entrances In both series, the same intended monomer/silica mass ratios of 0.50, 1.10, 1.40, 1.70, 2.00, and 2.60 were adjusted using proper masses of FA TA was used as the polyreaction catalyst at the constant molar ratio of TA/FA = 0.50 The cumulative mass of the solvent together with the monomer was kept constant at 50.00 g for each synthesis batch In the case of the T-series, additionally, anhydrous sodium sulphate was added as a desiccant agent at the constant molar ratio of Na2SO4/FA = 0.15 to provide an anhydrous reaction environment It traps the traces of water originating from toluene and monomer impurities as well as this one released in the FA polycondensation reaction Briefly, an amount of 1.50 g of SBA-15 held before at 200 ◦ C overnight was added under vigorous stirring (800 rpm) to a mixture of FA, solvent (water or toluene), TA, and Na2SO4 (solely in the case of the T-series) The mixture was placed in a two-neck round-bottom flask (100 cm3) immersed in an oil bath placed on a magnetic stirrer and equipped with a reflux condenser It was then agitated at room temperature for 30 min, and next a heating was turned on After the temperature of the reaction system reached 100 ◦ C, the mixture was isothermally held for the next 24 h under vigorous stirring (800 rpm) The resulting brownish com­ posite of poly(furfuryl alcohol) (PFA) and SBA-15 (PFA/SBA-15) was then isolated, washed with distilled water or toluene (depending on the reaction medium, respectively), and dried at 90 ◦ C overnight After­ wards, to remove the TA and Na2SO4 (undissolved in the original organic medium), the T-series materials were additionally washed with an abundant amount of hot distilled water (~60 ◦ C) and dried again at 90 ◦ C This step prevented the damage of the carbonizate structure caused by its high-temperature oxidation with sodium sulphate during branches of the nitrogen isotherms at p/p0 = 0.97–0.98 The micro- and mesopore volumes (Vμ and Vme, respectively) were extracted from yintercepts of tangents fitted to αs plots within αs = 0.35–1.30 and 1.70–2.50 (SBA-15 matrix), αs = 0.50–1.00 and 1.50–2.40 (PFA/SBA-15 carbonizates), and αs = 0.60–0.85 and 1.70–2.80 (carbon replicas), respectively For the SBA-15 matrix and carbonizates, the foregoing parameters were assessed with respect to the macroporous silica LiChrospher Si-1000 (SBET = 25 m2 g− 1) [51], while for the ultimate replicas, the non-porous carbon LMA10 was used as the reference [52] The main pore diameters (Dp) were extracted from pore size distribution curves (PSDs) In the case of SBA-15, the PSD was calculated using the non-local density functional theory model (NLDFT; adsorption branch; cylindrical pores assumption; software ASIQwin™ ver 1.11, Quan­ tachrome Instruments), while for carbonizates and carbon replicas the two-dimensional non-local density functional theory model devised for carbons possessing heterogeneous surfaces was applied (2D-NLDFT; SAIEUS software, ver 3.0) [53,54] Structural parameters were investigated by low-angle X-ray powder diffraction (XRD) using a Bruker D2 Phaser instrument equipped with a LYNXEYE detector The XRD patterns were recorded using Cu Kα radi­ ation (λ = 1.54184 Å) in the angular range of 2θ = 0.80–4.00◦ with a step of 0.02◦ Transmission electron microscopy (TEM) imaging was performed on an FEI Tecnai TF20 X-TWIN (FEG) microscope operated at an acceler­ ating voltage of 200 kV Before measurements, samples were dispersed in isopropanol followed by sonication for 10 and deposited onto carbon-coated copper TEM grids by the drop-casting technique Mid-infrared spectra (300 scans each) were collected in the spectral range of 650–4000 cm− at a resolution of cm− using a Nicolet iS5 (Thermo Scientific) FT-IR spectrometer equipped with a DLaTGS de­ tector A diffuse reflectance (DRIFT) device (EasiDiff™-Pike Technolo­ gies) and attenuated total reflectance kit (iD7 ATR Accessory, Thermo Scientific) for solid and liquid samples analyses were used, respectively Prior to the measurements, the solid materials, held before at 105 ◦ C for 72 h, were diluted with spectral grade dry KBr to wt% and gently milled in an agate mortar, while the ATR spectra for the liquid samples were acquired without dilution Average values of the ζ-potential (ZP) of SBA-15 immersed in pure reaction media (water and toluene) and respective FA solutions, were determined by using a Zetasizer Nano ZS instrument equipped with a maximum mW He–Ne laser, emitting at 633 nm (Malvern Instruments Ltd., Malvern, U.K.) The measurements were carried out using a Uni­ versal dip cell (ZEN1002) combined with a glass cuvette (PCS1115) Prior to the measurements, four suspensions containing 0.1 wt% of freshly calcined SBA-15 were prepared using distilled water, toluene, and corresponding 7.8 wt% solutions of FA The suspensions were son­ icated in an ultrasonic bath for 15 The analyses were performed at 25 ◦ C Before commencing the measurement, the sample’s temperature was allowed to equilibrate in the instrument chamber for Each analysis was repeated three times X-ray photoelectron spectroscopy (XPS) measurements were per­ formed on a Prevac photoelectron spectrometer equipped with a hemi­ spherical analyzer (VG SCIENTA R3000) using Al Kα rays (E = 1486.6 eV) as an X-ray radiation source at a constant pass energy of 100 eV for survey and high-resolution modes The powder composites were placed on a sample holder and introduced by a load lock into an analytical chamber with base pressure of × 10− mbar The binding energy scale was calibrated using the Si 2p line of pristine SBA-15 silica at 103.6 eV The surface composition was analysed on the base of the areas and binding energies of Si 2p, C 1s, and O 1s core levels The spectra were fitted using CasaXPS software version 2.3.23 An adsorptive interaction of the silica surface with FA in an aqueous medium was investigated employing total organic carbon (TOC) anal­ ysis using a Shimadzu TOC-VCPH apparatus Briefly, 1.0000 g of freshly calcined SBA-15 was immersed at room temperature (21 ◦ C) in 50.00 g of a 1.00 wt% FA-water mixture in a 100 cm3 round-bottom flask T carbonization as follows: Na2 SO4 + 4C ​ → ​ Na2 S + 4CO↑ The assynthesized composites were labelled as PFA/S-x_y, where x stands for the real PFA/SBA-15 mass ratio (determined based on TG measurements under an air atmosphere), and y refers to the series (y ≡ W and T for water and toluene medium, respectively) Additionally, two samples of bulky PFA were synthesized without using the silica matrix in water and toluene following the same protocol as for the composites These ma­ terials were labelled as PFA_W and PFA_T, respectively The PFA/S-x_y composites were carbonized in a tubular quartz furnace under an argon atmosphere (40 cm3 min− 1) at 850 ◦ C for h using a heating rate of β = ◦ C min− Finally, the silica matrix was removed by double etching with HF at room temperature for 90 Namely, 1.00 g of carbonizate was immersed in 30.0 cm3 of 5% HF solution and gently shaken ever and again The carbonizates and corresponding carbon replicas were marked as C/S-x_y and C-x_y, respectively 2.2 Characterization methods Textural parameters of materials were investigated by means of lowtemperature adsorption-desorption of nitrogen (− 195.8 ◦ C) The iso­ therms were collected using an ASAP 2020 sorptometer (Micromeritics) Prior to the analyses, the materials were evacuated at 250 ◦ C for h under vacuum The specific surface areas (SBET) were calculated ac­ cording to the Brunauer–Emmett–Teller model within p/p0 = 0.05–0.20, while the micropore surfaces (Sμ) were assessed based on the t-plot model (using the de Boer equation) at the same relative pressure range The external surface areas of SBA-15 and carbonizates (Sex) were computed from slopes of tangents fitted to αs plots within αs = 1.70–2.50 and 1.50–2.40, respectively The total pore volumes (Vt) were computed according to the single-point approach (s-p) from the adsorption R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 polarity of the reaction medium and the FA/SBA-15 ratio used Namely, in the case of the toluene series, the yield of polymerization is roughly two-threefold higher compared to that of the W-series (excepting the materials with the highest polymer content) This is reflected in a similar trend observed for the degree of filling of the pores, which for the Wseries varies between ca 10 and 73%, while for the T-series it spans in the range 28–68% It is pertinent to mention that the lower FA content, the higher polymerization efficiency is observed, notwithstanding the reaction medium (excepting the PFA/S-1.30_W composite; we reported on a similar effect in our previous works [50,70]) For the composites with the lowest PFA loading, it attained 34 and 99% for the W- and T-series, respectively This means that the use of toluene as the reaction medium facilitates definitely the successful incorporation of PFA to the channels of the silica matrix It is reasonable to conjecture that the effectiveness of silica decoration with PFA is governed by the following circumstances: (i) behavior of silica itself under harsh hydrothermal conditions of PFA deposition (SBA-15 undergoes partial leaching fol­ lowed by re-precipitation of silica resulting in the flattening of the inner surface corrugations [55]), (ii) state of the SBA-15 surface silanols in an aqueous and anhydrous environment and their likely role in the monomer pre-adsorption, (iii) mutual interaction between solvent and monomer molecules, (iv) catalyst acidic strength in these media, and (v) viscosity of the FA-solvent mixtures, which may play a crucial role in the kinetic of infiltration of the matrix pore system with carbon precursor [56] Surprisingly, this parameter was not discussed in the literature as far Herein, we have measured the viscosity of the studied synthesis systems The kinematic viscosity of the 7.80 wt% FA-water mixture at 21 ◦ C is equal to 1.14 mm2 s− 1, whereas for the FA-toluene mixture of the same concentration is 0.72 mm2 s− (for pure FA it equals 4.73 mm2 s− 1) Thus, this may be a hint unraveling the higher PFA loading within the T-series Interesting insights are provided by the analysis of the TG, DTG, and DTA curves (see Fig S1) Regardless of the reaction medium as well as the polymer content, the materials feature similar decomposition pro­ files with two distinctive stages (Fig S1, DTG profile) with the maxima centered at 340 and 520 ◦ C However, it is worth noting that in the DTG curves recorded for the composites of the W-series, the high-temperature maximum dominates, while the opposite situation is observed for the Tseries This suggests a slightly higher thermal stability of the W-series materials Furthermore, the differences in the manner of PFA deposition find reflection in the macroscopic images of the materials Namely, one can clearly see also the differences in the colors of the as-made composites (Fig S2) The brighter tints of the W-series materials may be seen at a glance even when the polymer content is higher than that one of the Tseries On one hand, this is indicative of a higher level of T-series PFA crosslinking On the other hand, this suggests another mechanism of polymer chain growth favoring the formation of chromophoric species (conjugated π-bond systems) in the T-series [57–60] It should be noted that this in turn may influence the carbonization of the polymer and the structural ordering of the final carbon material Fig Efficiency of FA polymerization and effectiveness of PFA deposition in the pore system of SBA-15 expressed as true PFA/SBA-15 mass ratio and pore filling degree (the shaded areas refer to the real PFA contents required for obtaining the respective replicas) equipped with a magnetic stirrer Then, the suspension was vigorously stirred (1000 rpm) for 30 After separation of silica by filtration on a Büchner funnel, the filtrate was subjected to the TOC analysis The capability of silica towards monomer adsorption was estimated based on a drop in the FA concentration during silica immersion compared to the mother liquor High-resolution thermogravimetric measurements (TG) were carried out using a SDT Q600 analyzer (TA Instruments) An amount of ca 20 mg of a sample was heated in a corundum cup from 30 to 980 ◦ C (β = 20 ◦ C min− 1) at an air atmosphere (100 cm3 min− 1) The true amounts of the carbon precursor incorporated into the silica matrices (i.e the real polymer/silica mass ratios in the PFA/SBA-15 composites) were calcu­ lated based on the mass loss related to the burning-off of the polymeric component regarding to the mass of the silica residue The silica’s pore filling degree was computed as a ratio of PFA volume (density of bulky PFA at room temperature, ρPFA = 1.55 g cm− [50]) with respect to the Vt of the silica matrix (expressed as a percentage) The same TG mea­ surement procedure was employed for the study on the thermo-oxidative stability of the ultimate carbon replicas Kinematic viscosity of the binary mixtures of FA with water and toluene was determined using a suspended-level (Ubbelohde) viscom­ eter The measurements were carried out at 21 ◦ C for the mixtures containing 7.80 wt% of the monomer This concentration corresponds to the mixtures used in the syntheses of the highest loaded composites 3.2 Textural and structural characteristics of C/S-x_y carbonizates and C-x_y replicas Results and discussion Textural and structural parameters of the parent silica matrix SBA-15 as well as the carbonizates and corresponding carbon replicas were investigated by low-temperature adsorption of nitrogen and low-angle X-ray diffraction The collected isotherms together with the corre­ sponding PSDs are depicted in Fig 2, while Fig displays the relevant XRD patterns The respective textural and structural parameters are gathered in Table For better readability, all results are presented along with the ascending real polymer loading The N2 adsorption isotherm for pristine SBA-15 is a textbook example of a IV(a) type with H1 hysteresis loop featuring steep parallel adsorption and desorption branches (cf Fig 2) [61] This evidences the 3.1 Effectiveness of PFA incorporation into SBA-15 mesochannels The efficiency of deposition of PFA inside the SBA-15 mesopore system was investigated by thermogravimetric measurements per­ formed under the oxidative atmosphere (i.e air) The calculated yield of polymerization as well as the true PFA/SBA-15 mass ratios and pore filling degrees are presented in Fig 1, while the recorded TG mass changes together with DTG and DTA curves are displayed in Supple­ mentary information section (Fig S1) The FA polymerization effectiveness is evidently influenced by the R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 Fig Nitrogen adsorption-desorption isotherms (A, B) and respective PSDs (A′ , B′ ) for C/S-x_y carbonizates (red lines and symbols) and corresponding C-x_y replicas (black lines and symbols) of W-series (A, A′ ): x = 0.17 (a), 0.28 (b), 0.35 (c), 0.39 (d), 0.43 (e), 1.30 (f), and T-series (B, B′ ): x = 0.49 (a), 0.73 (b), 0.94 (c), 1.02 (d), 1.10 (e), 1.22 (f) For clarity, the PSDs were offset of 0.25 (A′ ), and 0.60 cm3 g− nm− (B′ ) each (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.) presence of open-ended main mesopores uniform in diameter and long-range ordering of the architecture thereof These mesochannels are accompanied by a minor fraction of micropores which act as inter­ connecting channels The textural and structural parameters of the silica matrix are coherent with the typical values reported for SBA-15 in previously published papers [4,12,13,15,35,43,44,50,55] A very similar isotherm was recorded for the SBA-15@850 material Indeed, annealing at 850 ◦ C entailed the shrinkage of the structure, manifested R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 Fig Low-angle XRD patterns for C/S-x_y carbonizates (red lines) and corresponding C-x_y replicas (black lines) of W-series (A): x = 0.17 (a), 0.28 (b), 0.35 (c), 0.39 (d), 0.43 (e), 1.30 (f), and T-series (B): x = 0.49 (a), 0.73 (b), 0.94 (c), 1.02 (d), 1.10 (e), 1.22 (f) Reflections assignment: * ≡ (1 0), ^ ≡ (1 0), “ ≡ (2 0), # ≡ (2 0), $ ≡ (3 0) (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.) in narrowing mesopores by 0.8 nm and extinction of microporosity This in turn caused a drop in both SBET and Vt (cf Table 1) [15,50] In the case of the carbonizates of the W-series, except the material loaded with the highest amount of PFA (viz Fig 2A–a-e), the deposition of PFA followed by carbonization did not influence the nature of the isotherm The only differences are a slight shift of the hysteresis loop towards lower relative pressures caused by the thermal shrinkage of the SBA-15 structure during carbonization of the PFA/SBA-15, and a gradual decrease in both specific surface area and total pore volume with increasing PFA content (cf Fig 2A, Table 1) This is not surprising in view of the progressive filling of the silica’s pore system with carbon Interestingly, notwithstanding the pore filling degree, the pore size of the carbonizates remains roughly constant (ca 5.7–5.9 nm; Fig 2A’, Table 1) The N2 adsorption isotherm for the carbonizate containing the highest amount of the carbon precursor (Fig 2A–f) changes into the H2 (a) type with a characteristic desorption branch closure point at p/p0 ≈ 0.4 This points to the effect of cavitation of the adsorptive in partially blocked mesopores [61] This is clearly reflected in PSD, which reveals the shift in the main mesopore size to ca 5.2 nm (Fig 2A’–f, Table 1) Expectedly, the accumulation of carbonaceous material entailed a gradual decrease in the SBET and Vt, while increasing in the micropore volume This is a cumulative effect of the development of inherent microporosity in the carbonized PFA as well as the formation of slit-shaped micropores between the carbon material and silica wall due to their uncapping caused by discrepancies in the shrinkage effect dur­ ing carbonization [13–15,50] The two W-series samples with the lowest PFA contents (viz C0.17_W and C-0.28_W; Fig 2A–a,b) exhibit the N2 adsorption isotherms of type I(b), which is common for micro-mesoporous materials [61] The C-0.28_W material reveals additionally a narrow H4 hysteresis loop typical of suchlike mixed-porosity solids Indeed, both materials feature relatively low total pore volumes of 0.23 and 0.29 cm3 g− with 56 and 41% contributions of micropores, respectively (cf Table 1) The featureless XRD patterns for these carbons disclose the entirely disor­ dered structures thereof (Fig 3A–a,b) Other N2 adsorption isotherms of the W-series carbons may be classified as IV(a) type with H2(b) hysteresis loops For these samples, the adsorption branches show the presence of two inflections in the mesopore region (this is best seen in the case of the C-1.30_W replica), which confirm gradual development of two individual mesopore sys­ tems appearing along with increasing PFA content (cf Fig 2A’–c-e) Interestingly, simultaneous extinction of the microporosity is observed Considering the PSDs for C-1.30_W (Fig 2A’–f), it is evident that the primary mesopores originating from the removal of silica matrix walls centered at 3.1 nm are accompanied by far broader ones at ca 4.5–15.0 nm resulting from the coalescence of the adjacent pores of SBA-15, R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 Table Textural and structural parameters of parent SBA-15, SBA-15@850, C/S-x_y carbonizates, and corresponding carbon replicas Sample SBA-15 SBA-15@850 C/S-0.17_W C/S-0.28_W C/S-0.35_W C/S-0.39_W C/S-0.43_W C/S-1.30_W C-0.17_W C-0.28_W C-0.35_W C-0.39_W C-0.43_W C-1.30_W C/S-0.49_T C/S-0.73_T C/S-0.94_T C/S-1.02_T C/S-1.10_T C/S-1.22_T C-0.49_T C-0.73_T C-0.94_T C-1.02_T C-1.10_T C-1.22_T a b SBET (Sex)a [m2 g− 1] 886 (83) 642 (58) 517 (56) 524 (60) 464 (55) 465 (48) 455 (50) 302 (20) 385 441 732 755 927 855 282 (27) 344 (29) 284 (27) 372 (24) 302 (26) 69 (10) 1072 1779 2208 2033 1982 1222 Sμa [m2 g− 1] 34 0 18 24 28 101 261 223 109 178 167 13 53 34 103 49 280 0 0 73 Vtc [cm3 g− 1] Vμa [cm3 g− 1] 1.15 0.85 0.76 0.79 0.71 0.66 0.64 0.27 0.23 0.29 0.83 0.71 0.99 1.04 0.35 0.40 0.30 0.35 0.30 0.05 0.63 1.20 2.12 1.94 1.87 1.17 0.03 0.00 0.00 0.00 0.01 0.01 0.01 0.05 0.13 0.12 0.07 0.11 0.11 0.02 0.00 0.02 0.01 0.05 0.02 0.00 0.20 0.07 0.00 0.00 0.00 0.06 Vme [cm3 g− 1] a 1.02 0.78a 0.69a 0.71a 0.63a 0.60a 0.57a 0.20a 0.10b 0.17b 0.76b 0.60b 0.88b 1.02b 0.31a 0.34a 0.25a 0.27a 0.25a 0.04a 0.43b 1.13b 2.12b 1.94b 1.87b 1.11b Dp [nm] d 2.6; 7.6 3.0; 6.8d 3.9; 5.8e 3.9; 5.9e 3.9; 5.9e 3.9; 5.7e 3.9; 5.7e 5.2e – – 3.8; 5.5e 3.7; 5.5e 3.8; 5.5e 3.1; 6.9e 4.8e 4.7e 4.0e 4.1e 4.1e – – 2.9e 2.9; 4.1e 2.9; 4.1e 2.9; 4.0e 3.7e Dw [nm] f 3.1 2.7f – – – – – – – – – – – 5.9g – – – – – – – – 1.4h 1.4h 1.4h 5.7g a0i [nm] 10.7 9.5 10.0 9.8 9.9 9.7 9.7 9.8 – – – – – 9.8 9.5 9.6 9.8 9.8 9.7 – – – 9.8 9.8 9.7 9.5 αs model Vme = Vt ​ (s− p) − Vμ (αs) Single-point at p/p0 = 0.98 d NLDFT for silicas; adsorption branch; cylindrical pores assumed e 2D-NLDFT for carbons with heterogeneous surfaces f Silica wall thickness; Dw,sil = a0 − Dp ( )1 ρcarb − + Vμ g Carbon nanorod diameter; Dw,carb = c⋅d1 0 , c – constant; for cylindrical pores c = 1.213; d1 0 – interplanar spacing; d1 0 = 2⋅ d2 0 ; − Vme + ρcarb + Vμ − ρcarb – amorphous carbon density; ρcarb = 2.05 g cm [15,43,46] c / h Average thickness of carbon wall in the tube-type replicas; wC = (Dsil.850 − Din p p ) , Dsil.850 is the mesopore diameter of SBA-15@850; Din p p means the inner diameter of carbon tube i Due to the featureless XRD patterns in the (1 0) reflection region (Fig 3), the lattice parameters were calculated from (2 0) reflection; a0 = 4⋅ 3− which were previously either entirely empty or partially filled with the carbon precursor The width of this peak should not be surprising given the random distribution of PFA inside the SBA-15 pore system, which yields the pseudo-CMK-3 structures [15,50] Due to the defective struc­ ture, this material exhibits a slightly lower specific surface area than typical CMK-3, while its relatively high total pore volume of 1.04 cm3 g− is understandable Noteworthy, despite the non-ideality of these frameworks, their XRD patterns gradually take shape of the pattern of standard CMK-3 material along with increasing PFA loading, achieving the maximum similarity for the highest PFA content (Fig 3B–c-f) Recently, we reported on the formation of similar structures when SBA-15 with a low degree of silica framework condensation was employed as a hard template (therein, the silica matrix was detemplated under mild conditions using an acidified solution of KMnO4), and the deposition of PFA was carried out in water medium [15,50] However, it is pertinent to mention that using hydrochloric acid as a polyreaction catalyst leads to the formation of the typical CMK-3 structure [12,49] Another scenario was observed for the T-series carbonizates The two carbonizates with the lowest PFA loadings (i.e C/S-0.49_T and C/S0.73_T) show the N2 adsorption isotherms of type IV(a) with H1 hys­ teresis loops (Fig 2B–a,b) [61] It is worth noting that these loops are shifted to lower relative pressures compared to both SBA-15 and SBA-15@850, which suggests a progressive cladding of the inner walls of pores with the polymer Indeed, considering the corresponding PSDs (Fig 2B’–a,b), a gradual decrease in the diameter of the main mesopores with increasing PFA content is evident The materials with moderate PFA loadings (i.e C/S-0.94_T, C/S-1.02_T and C/S-1.10_T) feature the 1/2 ⋅ d2 0 isotherm of IV(a) type with a H2(a) hysteresis loop For these samples, the main pore size equals ca 4.0–4.1 nm regardless of the real content of the carbon precursor (Fig 2B’–c-e) The carbonizate with the highest PFA loading (C/S-1.22_T) shows the maximum nitrogen uptake close to nil (Fig 2B–f), which combined with the featureless PSD (Fig 2B’–f) clearly evidences its total pore filling with the polymer The XRD pat­ terns collected for the T-series carbonizates show lower intensity of the characteristic reflections compared to the parent silica, which proves filling the pores of the hard template with organic material (Fig 3B) The analysis of the behavior of the N2 adsorption isotherms recorded for the final carbon replicas of the T-series provides particularly inter­ esting conclusions The replicas derived from the two materials with the lowest PFA content disclose a micro-mesoporous character thereof (isotherm of type I(b) with a H4 loop), similar to the corresponding Wseries replicas (see Fig 2A–a,b, vs Fig 2B–a,b) [61] The lack of a long-range ordering of the architecture of these materials is visible in the low-angle XRD patterns (Fig 3B–a,b) Undoubtedly, a change is seen when considering the OMCs synthesized from the carbonizates of moderate PFA loadings (real polymer/silica ratio of 0.94–1.10, viz Fig 2B–c-e) Namely, the isotherms are of type IV(a) with H1 hysteresis loop and well-distinguished two inflections in the adsorption branch at ca p/p0 = 0.30–0.50, and 0.55–0.70 Apparently, this is reflected in the respective PSDs displayed in Fig 2B’–c-e, which show the bimodal mesoporosity of these materials featuring two maxima centered at 2.9 and 4.0–4.1 nm, typical of hollow-type CMK-5 carbon replica (Table 1) [18] The narrower pores originate from the leaching of silica matrix walls, while the broader ones are inherited from the carbonizate, in R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 Fig TEM images and Fourier diffractograms of carbon replicas: C-0.43_W (A), C-1.30_W (A′ ), C-1.10_T (B), and C-1.22_T (B′ ) which the inner silica walls were covered with a PFA film (intra-tubular carbon pores) Interestingly, the share of the latter one in the mesopore volume decreases with increasing content of carbon precursor (see Fig 2B’–c-e, decreasing the maxima at 4.0–4.1 nm), while the pore diameter stays constant Indeed, the bimodal porosity contributes to the exquisite development of the specific surface area exceeding 2200 m2 g− (cf Table 1) It should be underscored that such textbook examples of CMK-5 isotherms and PSDs were rarely reported in the literature The XRD patterns of these materials (Fig 3B–c-e) with five characteristic reflections including the dominating (1 0) one are indicative of the p6mm arrangement of the hollow-type carbon material [3,62] Thus, an excellent quality of the synthesized materials is evident It may be surprising that the T-series sample with the highest PFA loading yielded a high-quality rod-type CMK-3 replica, notwithstanding its pore filling degree barely equals 68% (see Figs 1, Fig 2B–f, Fig 2B’–f) However, given the thermal shrinkage of the SBA-15 structure during composite carbonization, this is understandable (such shrinkage causes a reduction in Vt roughly by ¼, cf Table 1) [15,50] This carbon replica features monomodal mesopores of 3.7 nm in diameter, a total pore volume of 1.17 cm3 g− 1, and SBET of 1222 m2 g− Such textural parameters are in accordance with previous reports on CMK-3 materials [3,4,6,9,10,12, 13,15,35,43,49,50] The structural ordering is manifested in the XRD pattern with three distinguished reflections, also typical of suchlike structures (Fig 3B–f) [34] R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 Fig DRIFT spectra collected for the SBA-15 after pre-adsorption of FA from water (A), and toluene (B) solutions (red lines) and after contact with pure solvents (black) followed by desorption at room temperature overnight (a), and at 50 ◦ C (b), 100 ◦ C (c), 150 ◦ C (d) for h The ATR spectra of pristine SBA-15, pure FA and respective solvents are added in the bottom (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.) The phase purity of the chosen carbon replicas was studied by highresolution thermogravimetric measurements at an air atmosphere [46] The relevant results are displayed in Fig S3 The narrower DTG curves for the T-series evidence the higher homogeneity (i.e lack of impurities being disordered carbonaceous material, which could be formed onto the external surfaces of silica matrix) of these materials compared to the W-series Interestingly, the later ones exhibit the same temperature of a maximum oxidation rate (ca 625 ◦ C) notwithstanding the PFA loading in the materials In contrast, the CMK-5 sample shows the maximum combustion rate at the temperature of ca 15 ◦ C lower This is justified by the open-work structure of this material mesoporosity and an excellent hexagonal arrangement (p6mm space group) This is in line with the N2 adsorption isotherms and XRD pattern (Fig 2B–e, Fig 2B’–e, Fig 3B–e) As expected, the higher loading of SBA-15 with PFA achieved in toluene results in the formation of a reg­ ular rod-type CMK-3 replica with a perfect hexagonal mesoscopic ar­ chitecture (Figs 4B’, 2B–f, 2B’–f and 3B–f) It should be emphasized that the analysis of the dozen TEM images of both materials from the T-series (not shown here) disclosed a lack of the effect of the formation of an external amorphous shell of the excessing PFA enveloping the PFA/silica composite particles Such a phenomenon was observed in the case of the highest-loaded materials synthesized in water as was reported in our previous works [12,15] Naturally, this influences positively the quality of the carbon replicas synthesized in toluene in terms of both structural ordering and textural parameters 3.3 Morphology of carbon replicas The structural ordering and morphology of the carbon replicas were investigated by TEM imaging The micrographs taken for the chosen materials of both series together with relevant Fourier diffractograms are displayed in Fig The images recorded for the carbon material based on the partially filled W-series composite (Fig 4A) reveal a poor ordering of the final structure (cf Fig 3A–e), although the Fourier diffraction pattern dis­ closes vestigial hexagonal architecture features This is coherent with the textural parameters (see Fig 2A–e, Fig 2A’–e) The higher degree of filling of the PFA matrix results in obtaining the pseudo-CMK-3 replica [15,50] As mentioned above, in this case, the carbon precursor fills the honeycomb pore system of SBA-15 randomly, i.e some channels remain empty, while others are partially or completely filled with PFA This may be seen in Fig 4A’ The darker and brighter regions correspond to car­ bon nanorods and cavities formed from empty pores, respectively Noteworthy, despite these structural discontinuities, such material is mesoscopically well ordered (cf Fig 2A–f, Fig 2A’–f, Fig 3A–f) More interestingly, the carbon structure derived from the partially filled composite of the T-series displays a fabulous TEM image taken along the [1 0] direction (Fig 4B) This is typical of a high-quality hollow-type CMK-5 replica with well-distinguished bimodal 3.4 Mechanism of PFA deposition: a spectroscopic study The substantial differences in the textural parameters of the W- and T-series OMCs were a premise suggesting different mechanisms of deposition of the carbon precursor depending on the polarity of the reaction medium This inspired us to deepen the study on the in­ teractions of monomer and polymer with the silica surface We put ef­ forts to unravel these issues by the investigation of FA-silica interactions (FT-IR) and analysis of the non-carbonized composites (FT-IR and XPS) 3.4.1 Monomer pre-adsorption The adsorptive interactions of silica surface with monomer and both reaction solvents were studied by means of DRIFT spectroscopy For this purpose, the freshly calcined silica (0.30 g) was immersed in 20.00 cm3 of wt% solutions of FA in water and toluene, respectively, at room temperature for h Additionally, to distinguish the silica-solvent in­ teractions, the SBA-15 matrix was contacted in the same manner with the pure solvents After the contact, the materials were separated without washing, dried at room temperature overnight, and then evac­ uated under static conditions at 50, 100, and 150 ◦ C for h The R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 adsorption capacity reached 0.29 μmol of the monomer per square meter of the silica surface Such a negligible monomer adsorption suggests the preferential adsorption of water This is in line with the above FT-IR study as well as the reports published elsewhere [65] Another scenario was observed when silica was immersed in pure toluene and the FA-toluene mixture (Fig 5B–a-d) The spectrum of the sample after the contact with pure solvent followed by evacuation at room temperature showed the complete loss of toluene Thus, the state of the freshly calcined silica surface was restored even for such mild desorption conditions The complete evaporation of the solvent at the temperature of ca 90 ◦ C below its boiling point (i.e 110 ◦ C) indicates a low affinity of toluene towards the silica surface Indeed, the phobic character of silica towards aromatics adsorption is not surprising [66] In contrast, the contact of SBA-15 with the FA-toluene mixture clearly revealed that the free silanols were involved in the attracting of the alcohol molecules This means that monomer adsorption is favored when toluene is used With this in mind, the formation of hollow-type carbon replicas as a result of polycondensation of the FA selectively adsorbed onto the silica surface appears understandable Moreover, the comparison of the intensity of FA bands adsorbed in water and toluene (see Fig 5A–a,d vs Fig 5B–a,d) confirms that the use of the aprotic medium promotes the adsorption of larger amounts of alcohol, which in turn is in line with the higher efficiency of PFA deposition in toluene (cf Fig 1) These findings were also proven by the measurements of the zeta potential of the parent silica immersed in pure reaction media and FA-solvent mixtures In contact with pure solvents, the SBA-15 silica revealed typical ZP values (− 31.3, and − 24.2 mV for water and toluene, respectively) [67,68] In contact with the FA solutions, the surface be­ comes depleted in a negative charge; in the case of FA-water, the ZP equaled − 6.7 mV, while for FA-toluene the ZP reached +12.9 mV This is due to the protonation of the free silanols by the FA molecules as follows: ≡ Si − OH+ : OR [69] 3.4.2 Surface chemistry of PFA/silica composites The DRIFT spectra of the as-made W- and T-series PFA/silica com­ posites with the highest PFA loading and respective bulk polymers are shown in Fig The curve-resolved C 1s regions of the corresponding XPS spectra are displayed in Fig S4, while the concentrations of particular carbon- and oxygen-containing surface moieties are gathered in Table S1 The spectrum recorded for the PFA/S-1.30_W composite is essen­ tially a simple superposition of the silica and bulk PFA spectra, excepting the 2800–3750 cm− region and the band at 979 cm− (Fig 6a) [70] The decrease in free silanol band intensity (3745 cm− 1) accompanied by the increase in the intensities of 2800–3750 cm− and 962 cm− modes may be assigned to the profound rehydration of the silica surface during the PFA deposition, which is not surprising taking into account its hy­ drothermal conditions (i.e 100 ◦ C, 24 h) The identical shape of the absorption modes of this composite and bulky PFA (Fig 6a,b, respec­ tively) confirms the lack of chemical anchoring of the monomer mole­ cules before the polyreaction (i.e the absence of the Si–O–C bridges that should be expected in this case) This ultimately proves the shielding role of water molecules occupying the adsorption sites on the silica surface The spectrum of the PFA/S-1.22_T composite discloses an increase in the intensity of 2800–3750 cm− band accompanied by the extinction of the 3745 cm− mode, while the intensity (and position) of the absorp­ tion at 979 cm− remains unaltered (Fig 6c) This suggests the engagement of isolated silanols in FA anchorage while lacking matrix rehydration, which is not surprising given the anhydrous conditions provided in the reaction system More interestingly, the PFA/S-1.22_T material features the disappearance of the 3120 cm− (− CH in furan ring) as well as 1560 and 1600 cm− bands (furan ring vibrations) This is due to the effect of the acid-catalyzed furan ring-opening leading to the formation of γ-diketone moieties, which is evidenced by the presence – O species) of an intense band at 1715 cm− (stretching vibrations of C– Fig DRIFT spectra of non-carbonized PFA/SBA-15 composites and bulk PFA samples: PFA/S-1.30_W (a), PFA_W (b), PFA/S-1.22_T (c), and PFA_T (d) The green line represents the spectrum of pristine SBA-15 (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.) collected DRIFT spectra are gathered in Fig The contact of the SBA-15 template with both pure water and the FAwater mixture resulted in rehydration of the silica surface This is manifested by a pronounced drop in the intensity of free silanols ab­ sorption at 3745 cm− accompanied by a significant increase in the in­ tensity of a broad band at 2800–3750 cm− ascribed to the stretching vibrations of hydrogen-bonded silanols, and shift of the stretching Si–O mode from 979 to 962 cm− (stretching Si–OH) (Fig 5A–a-d) [50,63] In the case of the silica immersed in FA-water mixture, the spectra reveal additionally the features of FA, namely, at 2929 and 2873 cm− (asymmetric and symmetric stretching of methylene bonds in –CH2–OH, – C stretching in the furan ring), 913 (out-of-­ respectively), 1505 (C– plane –CH deformation vibrations), and 744 cm− (out-of-plane –CH bending in furan ring) [64,65] Interestingly, the characteristic band assigned to strongly physically adsorbed water at 1625 cm− shows a lower intensity for the FA-water mixture This is the effect of competitive water-alcohol sorption as was reported elsewhere [63] Thus, the silica surface simultaneously attracts both water and FA with the engagement of free silanols However, the accessibility of adsorption sites for alcohol molecules is largely hindered by the shield of preferentially adsorbed water The desorption at elevated temperatures resulted in gradual extinction of the FA bands, but no surface dehydration was observed Indeed, it is impossible to reverse the silica hydration process under these conditions The interaction between silica and FA before the polycondensation reaction was proven by TOC analysis of the FA-water mixture after 30 of contact with freshly calcined SBA-15 It was found that the 10 R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 Fig Pictorial illustration of the postulated mechanism of PFA deposition in polar and nonpolar synthesis media and the structures of the resultant replicas Scheme Factors governing the formation of carbon replicas depending on the synthesis conditions: the synthesis pathways verified herein and in our previous reports [12,15,50] 11 R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 [70] Noteworthy, this effect was more profound for the T-series As a consequence of ring-opening reactions, the intensity of the 790 cm− band ascribed to 2,5-disubstituted furan rings in the PFA chain de­ creases These findings are in compliance with the XPS analysis (see Fig S4, Table S1) [64,71,72] Particularly interesting is the effect of the emerging of new bands at 1123 and 1195 cm− in the spectrum of the PFA/S-1.22_T composite (both absent for the W-series composite) This suggests the grafting of the polymer onto the silica surface by a Si–O–C covalent bond [73–76] This is coherent with the scenario anticipated from the textural pa­ rameters of the carbon replicas (cf Textural and structural characteristics of C/S-x_y carbonizates and C-x_y replicas) Namely, given the covalent anchoring of PFA when precipitated in toluene, the higher homogeneity of the polymer covering the silica walls is plausible This, in turn, leads to unraveling the excellent replication fidelity within the T-series ma­ terials and justifies the feasibility of manufacturing hollow replicas using a non-polar synthesis medium Interestingly, the XPS spectra did not reveal the presence of the Si–O–C moieties (Fig S4, Table S1) Most likely this is due to the polymer layer shielding the PFA-SiO2 interface It is pertinent to mention that in the spectrum of the PFA/S-1.22_T composite, the intensity of the silica bands within the range of 1000–1300 cm− is much lower compared to the PFA/S-1.30_W mate­ rial, although the latter one contains a higher amount of polymer This again supports the anticipated differences in the manner of polymer deposition (see Fig S2) The scheme illustrating the proposed mechanism of PFA precipita­ tion from polar and nonpolar media and the ultimate carbon structures are shown in Fig deposition of a polymer directly on the silica-solution interfacial Furthermore, the growth of polymer chains is not disturbed as it may occur, for instance, in the case of impregnation methods (evaporation of the solvent causes local fluctuations in the monomer concentration), thus creating the opportunity to ideally clad the matrix surface Sur­ prisingly, the level of silica matrix condensation and its pore diameter turned out to be not so determinative in this regard The results reported herein gave rise to anticipate that the use of nonpolar reaction medium and mildly acidic conditions may pave the way to develop a facile and versatile method for the synthesis of other ordered carbon mesostructures Conclusion This study was aimed at unraveling the true role of the reaction medium used for the nanoreplication of SBA-15 by the acid-catalyzed precipitation polycondensation of FA in the SiO2 matrix suspension For this purpose, two twin series of carbon replicas were synthesized by using water and toluene as dispersion media The comprehensive investigation of the textural and structural parameters, as well as the morphology of the polymer/silica carbonizates and respective replicas, disclosed that the polarity of the reaction medium plays a crucial role in the deposition of the polymer onto the SBA-15 surface Namely, in the polar solvent the polymer chains start propagating radially from the bulk monomer solution to the silica pore wall, while in the case of the nonpolar medium their growth occurs in the reverse direction This is due to the competitive monomer-solvent adsorption onto superficial SBA-15 silanols In the case of the aqueous system, H2O molecules are adsorbed preferentially forming a shield, which hinders the formation of a homogenous PFA layer, thus precluding the formation of a hollow-type replica Contrarily, when using the toluene-FA mixture, the monomer adsorption is favored The FA molecules anchor to the silica surface covalently and clad it evenly, therefore facilitating the formation of an excellent quality CMK-5 structure, rarely reported in the literature This finding may be a cornerstone to the development of simple and universal method for the synthesis of other OMCs This issue will be the subject of our forthcoming research 3.5 Other parameters affecting the structure of carbon replicas Combining the present research with our former findings [12,15,50] deeper insight into the influence of the synthesis conditions on the structure of the ultimate carbon replicas of SBA-15 can be drawn Namely, the following parameters have been investigated as far: (i) pore width of the SBA-15 matrix, (ii) degree of condensation of silanol groups of silica, (iii) acid strength of polycondensation catalyst, and (iv) po­ larity of the reaction medium All these parameters were examined for various degrees of pore filling in SBA-15 with PFA The verified mech­ anisms of carbon replicas formation depending on the combination of these parameters are depicted in Scheme The combination of using the silica matrix with broader pores and low degree of silica condensation (SBA-15 detemplated under mild conditions using an acidified solution of KMnO4 without further calci­ nation [50]) accompanied by employing the high polarity medium (water) and strong acid as a polycondensation catalyst (hydrochloric acid) led to the formation of the pseudo-CMK-3 structures notwith­ standing the real PFA loading (see Scheme 1, the green dash path) A similar scenario was observed in the present research for the route involving the use of highly condensed (calcined) silica featuring nar­ rower mesochannels, which was decorated with the carbon precursor in water under weak acidity (TA) (Scheme 1, green solid line path) Interestingly, modifying the latter route by using a strong acid (HCl) catalyst allows achieving a regular CMK-3 replica at higher PFA loading, although moderate amounts of polymer still yield pseudo-CMK-3 struc­ tures (Scheme 1, blue dash path) [12,15] Finally, it was found (in the present study) that employing toluene instead of water while replacing HCl with TA results in the formation of excellent structures of CMK-5 for moderate polymer loadings and CMK-3 replica for the complete pore filling with PFA (Scheme 1, red solid line) Given these findings, one may conjecture that the two substantial parameters driving the mechanism of PFA deposition and, consequently, tailoring the structure of carbon replicas, are the polarity of the PFA precipitation medium and the acidity of the polycondensation catalyst Indeed, it is beneficial to perform the PFA incorporation under anhy­ drous conditions using a mild acid catalyst, which favors even CRediT authorship contribution statement Rafał Janus: Conceptualization, Synthesis, Characterization, Writing – original manuscript, review & editing, Visualization, Formal ´­ analysis, Founding acquisition, Project administration Piotr Natkan ski: Characterization, Writing – original manuscript, review & editing Mariusz Wądrzyk: Writing – original manuscript, review & editing Marek Lewandowski: Writing – original manuscript, review & editing Piotr Łątka: Characterization Piotr Ku´strowski: Writing – original manuscript, review & editing Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper Acknowledgments The research was carried out using the infrastructure of the AGH Centre of Energy, AGH University of Science and Technology, as well as ´w The latter the Faculty of Chemistry, Jagiellonian University in Krako one was partially purchased thanks to the financial support of the Eu­ ropean Regional Development Fund in the framework of the Polish Innovation Economy Operational Program (contract No POIG.02.01.00-12-023/08) Part of the experiments was carried out thanks to the financial support of the National Science Centre in Poland under the grant No 2020/04/X/ST4/01697 R.J acknowledges the 12 R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 AGH University of Science and Technology for the financial support within the subsidy No 16.16.210.476 [20] R Wu, Q Ye, K Wu, H Dai, Potassium-modified ordered mesoporous carbon materials (K-CMK-3): highly efficient adsorbents for NO adsorption at low temperatures, J Solid State Chem 294 (2021), 121844, https://doi.org/10.1016/j jssc.2020.121844 [21] P Tan, Y Jiang, L.-B Sun, X.-Q Liu, K AlBahily, U Ravon, A Vinu, Design and fabrication of nanoporous adsorbents for the removal of aromatic sulfur compounds, J Mater Chem A (2018) 23978–24012, https://doi.org/10.1039/ C8TA09184F [22] W Su, X Lu, F Sheng, Y Sun, C Liu, G He, J Liu, X Wang, CO2 sorption properties over ordered mesoporous carbon CMK-3 in the presence of MDEA solution, J Chem Eng Data 63 (2018) 4779–4785, https://doi.org/10.1021/acs jced.8b00798 [23] Y Wang, X Bai, F Wang, H Qin, C Yin, S Kang, X Li, Y Zuo, L Cui, Surfactantassisted nanocasting route for synthesis of highly ordered mesoporous graphitic carbon and its application in CO2 adsorption, Sci Rep (2016), 026673, https:// doi.org/10.1038/srep26673 [24] T Yu, Q Li, X Zhao, H Xia, L Ma, J Wang, Y.S Meng, X Shen, Nanoconfined iron oxychloride material as a high-performance cathode for rechargeable chloride ion batteries, ACS Energy Lett (2017) 2341–2348, https://doi.org/10.1021/ acsenergylett.7b00699 [25] M.-S Kwon, A Choi, Y Park, J.Y Cheon, H Kang1, Y.N Jo, Y.-J Kim, S.Y Hong, S.H Joo, C Yang, K.T Lee, Synthesis of ordered mesoporous phenanthrenequinone-carbon via π- π interaction-dependent vapor pressure for rechargeable batteries, Sci Rep (2014) 7404, https://doi.org/10.1038/ srep07404 [26] N Ji, J Park, W Kim, CMK-5-based high energy density electrical double layer capacitor for AC line filtering, ACS Omega (2019) 18900–18907, https://doi org/10.1021/acsomega.9b03024 [27] C Zhang, Q Zhao, L Wan, T Wang, J Sun, Y Gao, T Jiang, S Wang, Poly dimethyl diallyl ammonium coated CMK-5 for sustained oral drug release, Int J Pharm 461 (2014) 171–180, https://doi.org/10.1016/j.ijpharm.2013.11.050 [28] M.V Kiamahalleh, A Mellati, S.A Madani, P Pendleton, H Zhang, S.H Madani, Smart carriers for controlled drug delivery: thermosensitive polymers embedded in ordered mesoporous carbon, J Pharm Sci 106 (2017) 1545–1552, https://doi org/10.1016/j.xphs.2017.02.010 [29] Q Zhao, Y Lin, N Han, X Li, H Geng, X Wang, Y Cui, S Wang, Mesoporous carbon nanomaterials in drug delivery and biomedical application, Drug Deliv 24 (2017) 94–107, https://doi.org/10.1080/10717544.2017.1399300 [30] X Peng, S.K Jain, J.K Singh, A Liu, Q Jin, Formation patterns of water clusters in CMK-3 and CMK-5 mesoporous carbons: a computational recognition study, Phys Chem Chem Phys 20 (2018) 17093, https://doi.org/10.1039/C8CP01887A [31] C Weinberger, M Hartmann, S Ren, T Sandberg, J.-H Smått, M Tiemann, Selective pore filling of mesoporous CMK-5 carbon studied by XRD: comparison between theoretical simulations and experimental results, Microporous Mesoporous Mater 266 (2018) 24–31, https://doi.org/10.1016/j micromeso.2018.02.035 [32] X Peng, S.K Jain, Understanding the influence of pore heterogeneity on water adsorption in realistic molecular models of activated carbons, J Phys Chem C 122 (2018) 28702–28711, https://doi.org/10.1021/acs.jpcc.8b09143 [33] W Schmidt, H Amenitsch, High dynamics of vapor adsorption in ordered mesoporous carbon CMK-5: a small angle X-ray scattering study, J Phys Chem C 124 (2020) 21418–21425, https://doi.org/10.1021/acs.jpcc.0c05356 [34] W Schmidt, Calculation of XRD patterns of simulated FDU-15, CMK-5, and CMK-3 carbon structures, Microporous Mesoporous Mater 117 (2009) 372–379, https:// doi.org/10.1016/j.micromeso.2008.07.020 [35] J Roggenbuck, G Koch, M Tiemann, Synthesis of mesoporous magnesium oxide by CMK-3 carbon structure replication, Chem Mater 18 (2006) 4151–4156, https://doi.org/10.1021/cm060740s [36] D Gu, W Schmidt, C.M Pichler, H.-J Bongard, B Spliethoff, S Asahina, Z Cao, O Terasaki, F Schüth, Surface-casting synthesis of mesoporous zirconia with a CMK-5-like structure and high surface area, Angew Chem Int Ed 56 (2017) 11222–11225, https://doi.org/10.1002/anie.201705042 [37] J Patra, P.C Rath, C.-H Yang, D Saikia, H.-M Kao, J.-K Chang, Threedimensional interpenetrating mesoporous carbon confining SnO2 particles for superior sodiation/desodiation properties, Nanoscale (2017) 8674–8683, https://doi.org/10.1039/c7nr02260c [38] S Jun, S.H Joo, R Ryoo, M Kruk, M Jaroniec, Z Liu, T Ohsuna, O Terasaki, Synthesis of new, nanoporous carbon with hexagonally ordered mesostructure, J Am Chem Soc 122 (2000) 10712–10713, https://doi.org/10.1021/ja002261e [39] S.H Joo, R Ryoo, M Kruk, M Jaroniec, Evidence for general nature of pore interconnectivity in 2-dimensional hexagonal mesoporous silicas prepared using block copolymer templates, J Phys Chem B 106 (2002) 4640–4646, https://doi org/10.1021/jp013583n [40] M Kruk, M Jaroniec, S.H Joo, R Ryoo, Characterization of regular and plugged SBA-15 silicas by using adsorption and inverse carbon replication and explanation of the plug formation mechanism, J Phys Chem B 107 (2003) 2205–2213, https://doi.org/10.1021/jp0271514 [41] S Che, A.E Garcia-Bennett, X Liu, R.P Hodgkins, P.A Wright, D Zhao, O Terasaki, T Tatsumi, Synthesis of large-pore Ia3d mesoporous silica and its tubelike carbon replica, Angew Chem Int Ed 42 (2003) 3930–3934, https://doi org/10.1002/anie.200351752 [42] Y Sakamoto, T.-W Kim, R Ryoo, O Terasaki, Three-dimensional structure of large-pore mesoporous cubic Ia3d silica with complementary pores and its carbon replica by electron crystallography, Angew Chem Int Ed 43 (2004) 5231–5234, https://doi.org/10.1002/anie.200460449 Appendix A Supplementary data Supplementary data to this article can be found online at https://doi org/10.1016/j.micromeso.2021.111542 References [1] R Ryoo, S.H Joo, M Kruk, M Jaroniec, Ordered mesoporous carbons, Adv Mater 13 (2001) 677–681, https://doi.org/10.1002/1521-4095(200105)13:93.0.CO;2-C [2] R Ryoo, S.H Joo, S Jun, Synthesis of highly ordered carbon molecular sieves via template-mediated structural transformation, J Phys Chem B 37 (1999) 7743–7746, https://doi.org/10.1021/jp991673a [3] R Ryoo, S.H Joo, Nanostructured carbon materials synthesized from mesoporous silica crystals by replication, Stud Surf Sci Catal 148 (2004) 241–260, https:// doi.org/10.1016/S0167-2991(04)80200-3 [4] B Szczę´sniak, J Choma, M Jaroniec, Major advances in the development of ordered mesoporous materials, Chem Commun 56 (2020) 7836, https://doi.org/ 10.1039/D0CC02840A [5] M Le˙za´ nska, P Pietrzyk, A Dudek, J Włoch, Nitration and reduction route to surface groups of mesoporous carbons obtained from sucrose and phloroglucinol/ formaldehyde precursors, Mater Chem Phys 149–150 (2015) 539–552, https:// doi.org/10.1016/j.matchemphys.2014.11.004 [6] K Yan, X Sun, S Ying, W Cheng, Y Deng, Z Ma, Y Zhao, X Wang, L Pan, Y Shi, Ultrafast microwave synthesis of rambutan-like CMK-3/carbon nanotubes nanocomposites for high-performance supercapacitor electrode materials, Sci Rep 10 (2020) 6227, https://doi.org/10.1038/s41598-020-63204-3 [7] C Weinberger, X Cao, M Tiemann, Selective surface modification in bimodal mesoporous CMK-5 carbon, J Mater Chem A (2016) 18426, https://doi.org/ 10.1039/C6TA07772B [8] M Tiemann, C Weinberger, Selective modification of hierarchical pores and surfaces in nanoporous materials, Adv Mater Interfaces (2021), 2001153, https://doi.org/10.1002/admi.202001153 [9] J.M Ju´ arez, B.C Ledesma, M G´ omez Costa, A.R Beltramone, O.A Anunziata, Novel preparation of CMK-3 nanostructured material modified with titania applied in hydrogen uptake and storage, Microporous Mesoporous Mater 254 (2017) 146–152, https://doi.org/10.1016/j.micromeso.2017.03.056 [10] P Janus, R Janus, P Ku´strowski, S Jarczewski, A Wach, A.M Silvestre-Albero, F Rodríguez-Reinoso, Chemically activated poly(furfuryl alcohol)-derived CMK-3 carbon catalysts for the oxidative dehydrogenation of ethylbenzene, Catal Today 235 (2014) 201–209, https://doi.org/10.1016/j.cattod.2014.03.019 [11] M Marciniak, J Goscianska, R Pietrzak, Physicochemical characterization of ordered mesoporous carbons functionalized by wet oxidation, J Mater Sci 53 (2018) 5997–6007, https://doi.org/10.1007/s10853-017-1960-2 [12] P Niebrzydowska, R Janus, P Ku´strowski, S Jarczewski, A Wach, A.M SilvestreAlbero, F Rodríguez-Reinoso, A simplified route to the synthesis of CMK-3 replica based on precipitation polycondensation of furfuryl alcohol in SBA-15 pore system, Carbon 64 (2013) 252–261, https://doi.org/10.1016/j.carbon.2013.07.060 [13] S Jarczewski, M Drozdek, P Michorczyk, C Cuadrado-Collados, J Gandara-Loec, J Silvestre-Albero, P Ku´strowski, Oxidative dehydrogenation of ethylbenzene over CMK-1 and CMK-3 carbon replicas with various mesopore architectures, Microporous Mesoporous Mater 271 (2018) 262–272, https://doi.org/10.1016/j micromeso.2018.06.007 [14] S Jarczewski, M Drozdek, A Wach, B Dudek, P Ku´strowski, M.E Casco, F Rodríguez-Reinoso, Dehydrogenation of ethylbenzene over poly(furfuryl alcohol)-derived CMK-1 carbon replica, Catal Lett 146 (2016) 1231–1241, https://doi.org/10.1007/s10562-016-1748-z [15] P Janus, R Janus, B Dudek, M Drozdek, A Silvestre-Albero, F RodríguezReinoso, P Ku´strowski, On mechanism of formation of SBA-15/furfuryl alcoholderived mesoporous carbon replicas and its relationship with catalytic activity in oxidative dehydrogenation of ethylbenzene, Microporous Mesoporous Mater 299 (2020), 110118, https://doi.org/10.1016/j.micromeso.2020.110118 [16] A Węgrzyniak, S Jarczewski, P Ku´strowski, P Michorczyk, Influence of carbon precursor on porosity, surface composition and catalytic behaviour of CMK-3 in oxidative dehydrogenation of propane to propene, J Porous Mater 25 (2018) 687–696, https://doi.org/10.1007/s10934-017-0482-2 [17] E Bjă ork, M.P Militello, L.H Tamborini, R.C Rodriguez, G.A Planes, D.F Acevedo, M.S Moreno, M Od´en, C.A Barbero, Mesoporous silica and carbon based catalysts for esterification and biodiesel fabrication – the effect of matrix surface composition and porosity, Appl Catal A 533 (2017) 49–58, https://doi.org/ 10.1016/j.apcata.2017.01.007 [18] Z Lei, S Bai, Y Xiao, L Dang, L An, G Zhang, Q Xu, CMK-5 mesoporous carbon synthesized via chemical vapor deposition of ferrocene as catalyst support for methanol oxidation, J Phys Chem C 112 (2008) 722–731, https://doi.org/ 10.1021/jp077322a [19] K Machowski, P Natka´ nski, A Białas, P Ku´strowski, Influence of thermal treatment conditions on efficiency of PFA/MCM-48 composite and CMK-1 carbon replica in adsorption of volatile organic compounds, J Therm Anal Calorim 126 (2016) 1313–1322, https://doi.org/10.1007/s10973-016-5614-4 13 R Janus et al Microporous and Mesoporous Materials 329 (2022) 111542 [43] R Janus, M Wądrzyk, M Lewandowski, P Natka´ nski, P Łątka, P Ku´strowski, Understanding porous structure of SBA-15 upon pseudomorphic transformation into MCM-41: non-direct investigation by carbon replication, J Ind Eng Chem 92 (2020) 131–144, https://doi.org/10.1016/j.jiec.2020.08.032 [44] A.B Fuertes, D.M Nevskaia, Template synthesis of mesoporous carbons from mesostructured silica by vapor deposition polymerisation, J Mater Chem 13 (2003) 1843–1846, https://doi.org/10.1039/B302659K [45] M Kruk, B Dufour, E.B Celer, T Kowalewski, M Jaroniec, K Matyjaszewski, Synthesis of mesoporous carbons using ordered and disordered mesoporous silica templates and polyacrylonitrile as carbon precursor, J Phys Chem B 109 (2005) 9216–9225, https://doi.org/10.1021/jp045594x [46] M Kruk, M Jaroniec, R Ryoo, S.H Joo, Characterization of ordered mesoporous carbons synthesized using MCM-48 silicas as templates, J Phys Chem B 104 (2000) 7960–7968, https://doi.org/10.1021/jp000861u [47] F Kleitz, S.H Choi, R Ryoo, Cubic Ia3d large mesoporous silica: synthesis and replication to platinum nanowires, carbon nanorods and carbon nanotubes, Chem Commun (2003) 2136–2137, https://doi.org/10.1039/B306504A [48] T.-W Kim, R Ryoo, K.P Gierszal, M Jaroniec, L.A Solovyov, Y Sakamoto, O Terasaki, Characterization of mesoporous carbons synthesized with SBA-16 silica template, J Mater Chem 15 (2005) 1560–1571, https://doi.org/10.1039/ B417804A [49] P Ku´strowski, R Janus, P Niebrzydowska, Method of synthesis of CMK-3-type carbon replica, U.S Patent 9,302,252 B2, April 5, 2016 [50] R Janus, P Natka´ nski, M Wądrzyk, B Dudek, M Gajewska, P Ku´strowski, Synthesis of pseudo-CMK-3 carbon replicas by precipitation polycondensation of furfuryl alcohol in the pore system of SBA-15 detemplated using KMnO4, Mater Today Commun 13 (2017) 6–22, https://doi.org/10.1016/j mtcomm.2017.07.009 [51] M Jaroniec, M Kruk, Standard nitrogen adsorption data for characterization of nanoporous silicas, Langmuir 15 (1999) 5410–5413, https://doi.org/10.1021/ la990136e [52] A Silvestre-Albero, J Silvestre-Albero, M Martínez-Escandell, R Futamura, T Itoh, K Kaneko, F Rodríguez-Reinoso, Non-porous reference carbon for N2 (77.4 K) and Ar (87.3 K) adsorption, Carbon 66 (2014) 699–704, https://doi.org/ 10.1016/j.carbon.2013.09.068 [53] J Jagiello, J.P Olivier, 2D-NLDFT adsorption models for carbon slit-shaped pores with surface energetical heterogeneity and geometrical corrugation, Carbon 55 (2013) 70–80, https://doi.org/10.1016/j.carbon.2012.12.011 [54] J Jagiello, J.P Olivier, Carbon slit pore model incorporating surface energetical heterogeneity and geometrical corrugation, Adsorption 19 (2013) 777–783, https://doi.org/10.1007/s10450-013-9517-4 [55] A Galarneau, M Nader, F Guenneau, F Di Renzo, A Gedeon, Understanding the stability in water of mesoporous SBA-15 and MCM-41, J Phys Chem C 111 (2007) 8268–8277, https://doi.org/10.1021/jp068526e [56] O Klepel, N Danneberg, M Suckow, M Erlitz, Carbon replicas of porous concrete obtained by chemical vapor deposition - some aspects of the synthesis mechanism, Mater Sci Appl (2017) 614–627, https://doi.org/10.4236/msa.2017.88043 [57] S Spange, B Heublein, A Schramm, R Martinez, Composites from furfuryl alcohol and inorganic solids by cationic initiation, General features, Macromol Chem., Rapid Commun 13 (1992) 511–515, https://doi.org/10.1002/ marc.1992.030131106 [58] S Spange, H Shütz, R Martinez, Composites from furfuryl alcohol and inorganic solids by cationic initiation, Spectroscopic studies of poly(furfuryl alcohol)-silica composites obtained by trifluoroacetic acid initiation, Macromol Chem 194 (1993) 1537–1544, https://doi.org/10.1002/macp.1993.021940602 [59] A Gandini, M.C Salon, M Choura, R El Gharbi, H Amri, Z Hui, Furan chemistry and ionic polymerization Mechanisms and structures, Macromol Chem., Macromol Symp 60 (1992) 165–176, https://doi.org/10.1002/ masy.19920600115 [60] M Choura, N.M Belgacem, A Gandini, Acid-catalyzed polycondensation of furfuryl alcohol: mechanisms of chromophore formation and cross-linking, Macromolecules 29 (1996) 3839–3850, https://doi.org/10.1021/ma951522f [61] M Thommes, K Kaneko, A.V Neimark, J.P Olivier, F Rodríguez-Reinoso, J Rouquerol, K.S.W Sing, Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report), Pure Appl Chem 87 (2015) 1051–1069, https://doi.org/10.1515/pac-2014-1117 [62] S.H Joo, S.J Choi, I Oh, J Kwak, Z Liu, O Terasaki, R Ryoo, Ordered nanoporous arrays of carbon supporting high dispersions of platinum nanoparticles, Nature 412 (2001) 169–172, https://doi.org/10.1038/35084046 [63] R Janus, M Wądrzyk, P Natka´ nski, P Cool, P Ku´strowski, Dynamic adsorptiondesorption of methyl ethyl ketone on MCM-41 and SBA-15 decorated with thermally activated polymers, J Ind Eng Chem 71 (2019) 465–480, https://doi org/10.1016/j.jiec.2018.12.004 [64] G Tondi, N Cefarin, T Sepperer, F D’Amico, R.J.F Berger, M Musso, G Birarda, A Reyer, T Schnabel, L Vaccari, Understanding the polymerization of polyfurfuryl alcohol: ring opening and Diels-Alder reactions, Polymers 11 (2019) 2126, https:// doi.org/10.3390/polym11122126 [65] K Machowski, P Ku´strowski, B Dudek, M Michalik, Elimination of ketone vapors by adsorption on spherical MCM-41 and MCM-48 silicas decorated with thermally activated poly(furfuryl alcohol), Mater Chem Phys 165 (2015) 253–260, https:// doi.org/10.1016/j.matchemphys.2015.09.026 [66] T Ncube, K.S.K Reddy, A Al Shoaibi, C Srinivasakannan, Benzene, toluene, mxylene adsorption on silica-based adsorbents, Energy Fuels 31 (2017) 1882–1888, https://doi.org/10.1021/acs.energyfuels.6b03192 [67] M Kokuneˇsoski, J Gulicovski, B Matovi´c, M Logar, S.K Milonji´c, B Babi´c, Synthesis and surface characterization of ordered mesoporous silica SBA-15, Mater Chem Phys 124 (2010) 1248–1252, https://doi.org/10.1016/j matchemphys.2010.08.066 [68] M Colilla, M Martínez-Carmona, S S´ anchez-Salcedo, M Luisa Ruiz-Gonz´ alez, J M Gonz´ alez-Calbet, M Vallet-Regí, A novel zwitterionic bioceramic with dual antibacterial capability, J Mater Chem B (2014) 5639–5651, https://doi.org/ 10.1039/C4TB00690A [69] M Kosmulski, E Matijevi´c, ζ-potentials of silica in water-alcohol mixtures, Langmuir (1992) 1060–1064, https://doi.org/10.1021/la00040a008 [70] R Janus, A Wach, P Ku´strowski, B Dudek, M Drozdek, A.M Silvestre-Albero, F Rodríguez-Reinoso, P Cool, Investigation on the low-temperature transformations of poly(furfuryl alcohol) deposited on MCM-41, Langmuir 29 (2013) 3045–3053, https://doi.org/10.1021/la3041852 [71] E Rodrigues Edwards, S.S Oishi, E Cocchieri Botelho, Analysis of chemical polymerization between functionalized MWCNT and poly(furfuryl alcohol) composite, Polímeros 28 (2018) 15–22, https://doi.org/10.1590/01041428.07016 [72] G.P L´ opez, D.G Castner, B.D Ratner, XPS O 1s binding energies for polymers containing hydroxyl, ether, ketone and ester groups, Surf Interface Anal 17 (1991) 267–272, https://doi.org/10.1002/sia.740170508 [73] T Yokoi, S Seo, N Chino, A Shimojima, T Okubo, Preparation of silica/carbon composites with uniform and well-ordered mesopores by esterification method, Microporous Mesoporous Mater 124 (2009) 123–130, https://doi.org/10.1016/j micromeso.2009.05.002 [74] N Guigo, A Mija, R Zavaglia, L Vincent, N Sbirrazzuoli, New insights on the thermal degradation pathways of neat poly(furfuryl alcohol) and poly(furfuryl alcohol)/SiO2 hybrid materials, Polym Degrad Stabil 94 (2009) 908–913, https://doi.org/10.1016/j.polymdegradstab.2009.03.008 [75] R Tian, O Seitz, M Li, W Hu, Y.J Chabal, J Gao, Infrared characterization of interfacial Si–O bond formation on silanized flat SiO2/Si surfaces, Langmuir 26 (2010) 4563–4566, https://doi.org/10.1021/la904597c [76] J Rao, Y Zhou, M Fan, Revealing the interface structure and bonding mechanism of coupling agent treated WPC, Polymers 10 (2018) 266, https://doi.org/10.3390/ polym10030266 14 ... synthesized in toluene in terms of both structural ordering and textural parameters 3.3 Morphology of carbon replicas The structural ordering and morphology of the carbon replicas were investigated by. .. not surprising in view of the progressive filling of the silica’s pore system with carbon Interestingly, notwithstanding the pore filling degree, the pore size of the carbonizates remains roughly... Namely, 1.00 g of carbonizate was immersed in 30.0 cm3 of 5% HF solution and gently shaken ever and again The carbonizates and corresponding carbon replicas were marked as C/S-x_y and C-x_y, respectively