Copper benzene-1,3,5-tricarboxylate (HKUST-1) is one of the materials holding the greatest potential for clean energy gases among microporous storage materials. Although this material is commercially available as a powder with particle size 10–20 μm, for easier handling adsorbents are preferentially employed as pellets or monoliths.
Microporous and Mesoporous Materials 316 (2021) 110948 Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: http://www.elsevier.com/locate/micromeso Copper benzene-1,3,5-tricarboxylate (HKUST-1) – graphene oxide pellets for methane adsorption ´n a, Janos Madar ărgy Sa fran c, Ying Wang d, Krisztina La ´szlo ´ a, * Andrea Doma asz b, Gyo a Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, Budafoki út 8., Budapest, H, 1521, Hungary Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szt Gell´ert t´er 4., Budapest, H, 1521, Hungary c Research Institute for Technical Physics and Materials Science, Eă otvă os Lor and Research Network, Konkoly Thege M út 29-33., H-1121, Budapest, Hungary d College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China b A R T I C L E I N F O A B S T R A C T Keywords: MOF MOF-GO composite Adsorption XRD Compression Gas storage Copper benzene-1,3,5-tricarboxylate (HKUST-1) is one of the materials holding the greatest potential for clean energy gases among microporous storage materials Although this material is commercially available as a powder with particle size 10–20 μm, for easier handling adsorbents are preferentially employed as pellets or monoliths Even under binder free conditions there could be a high price to pay for compacting: loss in crystallinity and in porosity To determine the protection potential of graphene oxide (GO) a HKUST-1@GO composite was studied The material of 16% GO was obtained in a single step solvothermal synthesis The pristine HKUST-1 as well as HKUST1@GO formed consistent, integrated pellets when compressed at 25 and 50 bar without any binder PowderXRD and N2 adsorption were used to monitor the changes in crystallinity and pore structure It was found that GO has a protective effect against the 25 or 50 bar applied pressure, as 75% of the pore volume and the apparent surface area is saved in HKUST1@GO (vs 43% and 47%, respectively, in HKUST-1) after compression Presumably, the flexible GO sheets with high mechanical stability act as compressible spacers between the crystals thus preventing their amorphisation Comparison of the adsorption properties of the HKUST-1 and HKUST-1@GO powders and pellets revealed that the performed compression deteriorated the structure of the MOF and thus reduced the CH4 uptake Further studies are needed to optimize the compression pressure for a more reasonable loss in the gas uptake capacity Introduction Cleaner combustion natural gas and bio gas as alternative fuels could significantly reduce environmental stress from carbon dioxide and other emissions [1] Current high-pressure and cryogenic gas storage methods however are not economically ideal for the storage and transport of these gases Adsorption gas storage may offer attractive solutions for their capture and portable storage For cost effective implementation of this technology suitable nanoporous adsorbents are required [2,3] The American Department of Energy (DOE) has established the gravimetric and/or volumetric methane adsorption capacities necessary for adsor bents (263 cm3 CH4/cm3 adsorbent) [4,5] Metal organic frameworks (MOFs) with outstanding gas adsorption properties are among the most promising materials for this purpose, thanks to their permanent microporosity and outstanding apparent surface area Their hybrid three dimensional open framework with or dered open pore structure is constructed from multivalent metal ions or clusters connected by organic ligands via coordination bonds [6–8] Copper benzene-1,3,5-tricarboxylate or HKUST-1 (named after Hong-Kong University of Science and Technology) [9] attracts special attention among MOFs because its volumetric methane adsorption ca pacity has actually reached the DOE target [10] HKUST-1 is composed of copper (II) ions and benzene-1,3,5-tricarboxylate (btc3− ) organic li gands In its paddle-wheel secondary building unit (SBU) two copper (II) ions form coordination bonds with one of the carboxylate groups of four btc3− ligands, leaving one unsaturated open metal site on each copper It is commercially available as Basolite C300 However, the sensitivity of the as received HKUST-1 in its powder form to humid environment and its moderate thermal conductivity present a formidable technical chal lenge to its applications as an adsorption gas storage vehicle * Corresponding author E-mail addresses: doman.andrea@mail.bme.hu (A Dom´ an), madarasz@mail.bme.hu (J Madar´ asz), safran.gyorgy@energia.mta.hu (G S´ afr´ an), yingwang@tongji edu.cn (Y Wang), klaszlo@mail.bme.hu, klaszlo@mail.bme.hu (K L´ aszl´ o) https://doi.org/10.1016/j.micromeso.2021.110948 Received 25 September 2020; Received in revised form 31 January 2021; Accepted February 2021 Available online February 2021 1387-1811/© 2021 The Authors Published by Elsevier Inc This is an open (http://creativecommons.org/licenses/by-nc-nd/4.0/) access article under the CC BY-NC-ND license A Dom´ an et al Microporous and Mesoporous Materials 316 (2021) 110948 Fig Characterisation of HKUST-1 and HKUST-1@GO samples: (a) powder XRD pattern of the air-dried material; (b) TG and (d) DTG curves from the thermal analysis of the samples up to 800 ◦ C in air flow (130 cm3/min) at heating rate 10 ◦ C/min; (c) low temperature (− 196 ◦ C) nitrogen adsorption/desorption isotherms and (d) TEM image of HKUST-1 powder route to prepare HKUST-1 pellets is by densification of pre synthetized HKUST-1 powder Pelletisation has further potential advantages, like enhancement in mechanical strength, thermal conductivity, chemical stability, packing and volumetric density Mechanochemically assisted methods were found effective in the synthesis of carbon materials with enhanced gas uptake capacity [15–17] However, the most commonly observed response of HKUST-1 under high external pressure is amorphisation, which results in an unfavourable reduction of surface area and pore volume [10,18–25] For instance, Kim et al compacted activated (100 ◦ C, h) HKUST-1 powder (1737 m2/g) at 25–340 bar for 10 and found a decrease in crystallinity and surface area with increasing pressure The loss in SBET was 34% already at 25 bar While partial structural damage through collapse was observable only above 100 bar, 340 bar resulted in almost total collapse of the pore system [21] Addition of polyvinyl alcohol (PVA) binder in the HKUST-1 pellets led to a moderate surface area of 963 m2/g, probably because the PVA molecules partially occupied the pore system of HKUST-1 [20] This result supports the standpoint that, although binders can enhance the mechanical or even the thermal stability, free pellets are more desirable to preserve the excellent adsorption properties of MOFs Dhainaut et al pelletised HKUST-1 (and also UiO-66, UiO-67, UiO-66-NH2) powders with and wt% expanded natural graphite (ENG) binder at up to 1210 bar Obviously, simply mixing HKUST-1 with ENG resulted in a limited decrease of SBET from 1288 m2/g (no ENG added) to 1246 m2/g (1 wt% ENG) and 1105 m2/g (2 wt% ENG), since the surface area of graphite lags behind that of HKUST-1 The surface area of the composite systems decreased further with increasing pressure Maximum losses of ca 25, 23 and 26% were observable at the highest pressures in the binder free pellets and in samples with wt% and wt% ENG content, respectively [23] Various groups report contradictory findings regarding the level of pressure induced amorphisation either in lab made HKUST-1 [10,19,21, 23] or in commercially available Basolite C300 powder [22,24,25] Dhainaut et al suggested that the amorphisation depends at least partly on the compression protocol Therefore results obtained in an uncon trolled or poorlycontrolled densification manner should be interpreted with care [23] However, Terracina et al prepared tablets from com mercial Basolite C300 powder using a pill maker, operating with a hy draulic press They found that 400 bar is required to form mechanically stable tablets In a unique way, they have observed, that the specific Fig Effect of water vapour on HKUST-1 powder; (a) water vapour adsorp tion/desorption isotherm (20 ◦ C) of HKUST-1 SEM images of the (b) as received and (c) the aged (85% relative humidity RH 20 ◦ C 21 days) samples Fig HKUST-1 and HKUST-1@GO (16 wt% GO) pellets formed under 25 or 50 bar Several attempts have been made to form more desirable HKUST-1 monoliths such as by sol-gel synthesis [11], Cu(OH)2 monolith conver sion [12], 3D printing [13] or powder packing [14] The most common A Dom´ an et al Microporous and Mesoporous Materials 316 (2021) 110948 Fig Comparison of the XRD pattern of the powder and compressed (a) HKUST-1 and (b) HKUST-1@GO Table Data from low temperature (− 196 ◦ C) nitrogen adsorption isotherms and methane uptake values of HKUST-1 and HKUST-1@GO powder and pellets at 1000 mbar Sample Nitrogen SBET HKUST-1 powder HKUST-1_25 HKUST-1_50 HKUST1@GO powder HKUST1@GO_25 HKUST1@GO_50 Methane uptake at 1000 mbar Vtot Vmicro ◦C − ◦C cm (STP)/g mg/ g cm3 (STP)/g mg/ g 0.55 32.6 23.3 39.6 28.3 0.39 0.25 0.65 0.36 0.24 0.57 28.1 23.8 30.6 20.1 17.0 21.8 32.9 27.4 37.8 23.5 19.6 27.0 1110 0.46 0.41 28.5 20.3 34.6 24.7 1130 0.47 0.42 27.0 19.3 31.8 22.7 m / g cm /g 1500 0.62 970 620 1550 group [29] The effect of the external pressure (25–200 bar) was compared in a physical HKUST-1+CA mixture to HKUST-1@CA (both with a mass ratio 1:1) In the latter the MOF crystals were grown on CA under solvothermal conditions The nanoscale structure of HKUST-1+CA is more sensitive to the external pressure, but at higher compressions HKUST-1 loses its crys talline structure also in the composite sample No significant difference was found between the corresponding CH4 adsorption isotherms of the composites, either in the as-prepared samples or after compression at 100 bar After exposure to higher external pressure the CH4 uptake seems to be governed by the MOF Graphene oxide (GO) was found to improve the methane adsorption properties of HKUST-1 [30,31] GO is a single or oligo-layer graphene decorated with various oxygen containing functional groups (e.g hy droxyl, carboxyl, epoxide groups) [32] The functional groups make it possible to produce stable aqueous graphene oxide suspensions, which, furthermore, can be reactive [33] In this paper, we report a new synthesis route to prepare HKUST1@GO composites Although HKUST-1 - GO systems were studied earlier, e.g., by Xu et al [34], we propose a novel synthesis route by circumventing the drying step at the end of the improved Hummers exfoliation The copper salt was directly mixed with the diluted GO suspension instead of using dry GO Using this technique the ultrasound assisted tedious re-suspension step of the GO can also be avoided The protective effect of GO during the pelletisation HKUST-1@GO is inves tigated Methane adsorption properties of the HKUST-1 and HKUST-1@GO powders and pellets are compared Fig Low temperature (− 196 ◦ C) nitrogen adsorption/desorption isotherms of the powder and compressed HKUST-1 and HKUST-1@GO samples Red circle highlights the fine structure of the corresponding isotherms (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) surface area increased in the pelletising process by 15% from 1620 to 1935 m2/g [26] Nanostructured carbon support can potentially improve the me chanical stability and the thermal conductivity, and moreover enhance the water resistance and/or gas adsorption capacity by a synergistic effect [27,28] The protective effect of a resorcinol – formaldehyde based carbon aerogel (CA) support was studied earlier in two different forms by our A Dom´ an et al Microporous and Mesoporous Materials 316 (2021) 110948 Fig Integral (a, b) and differential (c, d) pore size distributions calculated from the adsorption branch of the nitrogen adsorption isotherms Fig SEM images of the HKUST-1@GO sample Powder (a); surface (b) and inside (c) after compression at 25 bar; surface (d) and inside (e) after compression at 50 bar A Dom´ an et al Microporous and Mesoporous Materials 316 (2021) 110948 Fig Atmospheric (up to 1000 mbar) methane adsorption isotherms of HKUST-1 and HKUST-1@GO powders and pellets (a) at ◦ C and (b) at − ◦ C Approximately 100 mg non-activated samples were placed in a 13 mm diameter sample holder and kept at the required pressure for 10 The compressed samples were designated by sample name and applied pressure HKUST-1_25 thus refers to HKUST-1 compressed at 25 bar 2.2 Methods Scanning electron microscopy (SEM, JEOL JSM 6380LA) was used to characterize the morphology of the samples Gold coating was applied to increase the conductivity of the samples Conventional and high reso lution transmission electron microscopy (200 kV Philips CM20 TEM and 300 kV JEOL 3010 HRTEM) were used to image the morphology, grain and grain size distribution of the samples For TEM and HRTEM imaging the samples were drop-dried on carbon-coated microgrids XRD patterns were obtained in the range 2θ = 4◦ –84◦ with an X’pert Pro MPD (PANalytical Bv., The Netherlands) X-ray diffractometer using an X’celerator type detector, Cu Kα radiation with a Ni filter foil (λ = 1.5408 Å) and a “zero-background" Si single crystal sample holder Phase identification was assisted by the Search&Match algorithm of the HighScore Plus (PANalytical Bv., The Netherlands) software, based on either the international Powder Diffraction File (PDF4+, Release 2020, International Centre of Diffraction Data, ICDD, Pennsylvania, USA), or The Cambridge Structural Database (CSD-Enterprise, version 5.42, Cambridge Crystallographic Data Centre, CCDC [41]) using the built-in powder pattern generator algorithm of the Mercury program [42] The thermal behaviour of the samples was investigated by simulta neous thermogravimetry/differential thermal analysis (TG/DTA; STD 2960 Simultaneous DTA-TGA, TA Instruments) The measurements were carried out in dry air flow of 130 cm3/min (heating rate 10 ◦ C/min) Nitrogen adsorption/desorption isotherms were measured at − 196 ◦ C by a NOVA 2000e (Quantachrome, USA) volumetric computercontrolled surface analyser All the samples were outgassed in vacuum at 110 ◦ C (activation) prior to the nitrogen adsorption measurements The apparent surface area SBET was calculated using the Brunauer-EmmettTeller (BET) model [43] The total pore volume Vtot was derived from the amount of N2 adsorbed at relative pressure p/p0 → 1, assuming that the pores were filled with liquid adsorbate The micropore volume Vmicro was obtained from the Dubinin-Radushkevich (DR) plot [44] The pore size distribution was calculated with the Barett-Joyner-Halenda (BJH) method The validity of this process is limited to the range 2–50 nm Transformation of the primary adsorption data was performed with the Quantachrome ASiQwin software (version 3.0) Water vapour adsorption/desorption isotherms were measured by a Fig Comparison of the methane uptake of HKUST-1 and HKUST-1@GO powders and pellets at ◦ C and − ◦ C at 1000 mbar Experimental 2.1 Materials The improved Hummers’ method was used to prepare the GO [35, 36] After thorough purification a 1.1w/w% aqueous suspension was obtained [37] The GO was used in this suspended form HKUST-1 (C18H6Cu3O12, M: 604.87 g/mol) was synthesized under solvothermal conditions following Wang et al [38,39] The benzene-1, 3,5-tricarboxylic acid (H3BTC) was dissolved in ethanol and then mixed with the stoichiometric amount of Cu(NO3)2⋅3H2O dissolved in MilliQ water After 10 argon gas was bubbled through the mixture for to eliminate air from the autoclave prior to sealing The mixture was kept at 80 ◦ C for 24 h The obtained turquoise crystals were washed with ethanol three times and dried in air at ambient conditions for 24 h The samples were stored for further use in a desiccator filled with freshly activated silica The HKUST-1@GO composites were pre pared in the same way, but instead of pure water a g/dm3 GO sus pension was used as solvent for the copper salt and as GO source [40] Air-dried samples were homogenized in a mortar before further measurements HKUST-1 and HKUST-1@GO samples were compressed under 25 and 50 bar using an OL57 hydraulic press (Manfredi, Pinerolo, Italy) A Dom´ an et al Microporous and Mesoporous Materials 316 (2021) 110948 Hydrosorb-1 (Quantachrome, USA) volumetric computer-controlled surface analyser at 20 ◦ C, up to 1000 mbar The samples were out gassed in vacuum at 180 ◦ C prior to the measurement Methane adsorption/desorption isotherms were measured at and − ◦ C with an AUTOSORB-1 (Quantachrome, USA) computer-controlled analyser many cases that application of high external pressure to MOFs can result in anomalous mechanical behaviour [18,47] For this reason the HKUST-1@GO composite was compressed to reveal the mechanical behaviour of the associated system during the compression The pristine HKUST-1, as well as the GO derivative, formed consistent, integrated pellets when compressed at 25 and 50 bar (Fig 3) The characteristic XRD pattern of HKUST-1 is clearly retained after the compression of the powders (Fig 4a and b) The peak positions in the compressed materials are slightly shifted to higher angles, implying a decreased interplanar distance Peak widening and baseline increase however indicate a certain level of structural damage These phenomena were not observed in HKUST-1@GO_25 Instead, the increased relative intensity of the (222) reflection at 2θ = 12◦ of this sample implies that during the compression individual HKUST-1 crystals rotated into a preferred direction due to GO The adsorption isotherms show that the microporous character of all the samples is preserved after the compression, in spite of the significant decrease in the apparent surface area (SBET), total and micro pore vol ume (Vtot and Vmicro, respectively) (Fig 5, Table 1) The linear range of the BET representation was located with the procedure proposed by Rouquerol et al [48] The main criteria of the procedure were met in the p/p0 = 0–0.02 range As no kernel files necessary for DFT based calcu lations are available for the HKUST-1@GO systems, the BJH method, limited to the mesopore range, was employed to calculate the pore size distributions (PSDs) (Fig 6) The uncompressed samples show a bimodal pore size distribution as implied by the fine distinct structure high lighted in the isotherms Both the isotherms and the PSDs reveal that the addition of GO moderates the effects of the compression In the iso therms of the pellets the fine structure at p/p0 < 0.1 disappears This phenomenon results in the simplification of the distribution functions in Fig c and d The SEM images in Fig confirm that the surface and the internal morphology of the HKUST-1 and its composites are altered after the compression On comparing the parameters that characterize the pore structure (SBET, Vtot and Vmicro in Table 1) of HKUST-1 powder and pellets the overall loss in porosity increases linearly with the pressure By contrast, in the associated system the loss is notably smaller and is not influenced by the compression pressure Presumably, the flexible GO sheets with high mechanical stability act as compressible spacers between the crystals thus preventing their degradation Results and discussion 3.1 Characterisation of the samples The pristine HKUST-1 powder was obtained with a yield of 84% (solvent free MOF) The crystalline structure of the turquoise product was identified by powder XRD phase analysis (Fig 1a) Its thermal decomposition in oxidative atmosphere (Fig 1b) shows three well distinguishable mass loss steps The first up to 150 ◦ C corresponds to water release from the pore network, the second (150–250 ◦ C) to the exile of strongly bonded water and the thermal decomposition of the ester groups decorating the carboxylic groups not bonded to the copper, and the third, around 300 ◦ C, to thermal degradation of the organic linker [39] The low temperature nitrogen adsorption/desorption isotherm is of Type Ib according to the recent IUPAC classification [45], characteristic of exclusively microporous systems (Fig 1c) The nano sized crystalline particles of HKUST-1 are clearly recognisable on the HRTEM image (Fig 1d) Although HKUST-1 is an outstanding candidate for methane and natural gas storage, this application is seriously challenged by its vulnerability to the presence of water either in liquid or vapour form (Fig 2) The water uptake of HKUST-1 substantially exceeds that of nitrogen, and part of the water remains irreversibly sorbed under the condition of the last point of the desorption branch (vacuum, 20 ◦ C) The air dried HKUST-1 contains ca 9.4 mol/unit water Part of this water fills the pores as “bulk” water and mol/unit is related to the free Cu sites The presence of the water results in a slow decomposition of the MOF with an estimated half-life of about 33 months Exposure to high relative humidity accelerates the degradation (Fig inset) [46] In our previous work, we reported that graphene oxide is able to improve the water resistance of HKUST-1 when used in combination [40] It was reported earlier that acidic surface groups are advantageous for the formation of HKUST-1 [29] Therefore HKUST-1@GO compos ites were prepared in water – ethanol binary solvent It was found that the GO can, at least partially, save the metal – linker coordination bonds by sacrificing the ester groups, formed between ethanol and the carboxyl groups on the GO sheets during the solvothermal synthesis The XRD pattern of the HKUST-1@GO system confirmed that the octahedral HKUST-1 crystals were successfully formed also in the presence of g/dm3 GO (Fig 1a) with a yield of 82% The GO content in the solvent-free HKUST-1@GO system was 16 wt% The thermal behaviour of the composites is similar to that of pristine HKUST-1 (Fig 1b) Since GO adheres well to HKUST-1 crystals and is well distributed in the system, the thermal decomposition of the MOF also facilitates the disintegration of GO GO therefore burns out simulta neously with HKUST-1 at around 300 ◦ C, at a much lower temperature than when it is alone The highly microporous nature of HKUST-1 is preserved even after its association with GO (Fig 1c) However, the adsorption/desorption isotherm of HKUST-1@GO exhibits a flat, elon gated hysteresis loop of Type H4 [45] This indicates a certain degree of mesopore formation, presumably in the interface of aggregated compounds 3.3 Adsorption of methane The effect of pelletisation on the methane adsorption capacity is of primary importance for gas storage application The methane adsorption performance of the powders and the compressed pellets was measured at ◦ C and − ◦ C Fig compares the atmospheric methane isotherms of the various samples The shape of all the isotherms reflects reversible adsorption The adsorption capacities at 1000 mbar equilibrium pres sure are compared in Fig Table also reports these capacities in mg/g units The volumes found for the associated systems exceed those of the pristine HKUST-1 pellets at both temperatures in the whole pressure range The loss in methane uptake is proportional to the applied pressure not only for HKUST-1 but also for HKUST-1@GO At both temperatures the effect of pressure is about twice as great for the pristine MOF The added GO enhances the pressure tolerance particularly at the higher compression applied As already proposed, the flexible GO sheets act as compressible spacers thus preventing amorphisation of the crystals 3.2 Compression Conclusions For easier handling, adsorbents are preferentially employed as pel lets or monoliths The compression step is intended to reduce the space between individual crystals without destroying their structure and, if possible, to increase the adsorption capacity It has been reported in HKUST-1 is one of the outstanding candidates for adsorption gas storage on account of its excellent methane uptake, but its powder re quires compaction to allow it to be easily handled During the pellet isation process, however, a significant part of the pore volume is lost A Dom´ an et al Microporous and Mesoporous Materials 316 (2021) 110948 This article describes how HKUST-1@GO (with 16% GO) was prepared in powder form with solvothermal self-assembly of the MOF using a ca 1% aqueous GO suspension as solvent for the copper salt Pristine HKUST-1 and HKUST-1@GO were pelleted and the effect of the external pressure (25 and 50 bar) was investigated Both the pristine HKUST-1 as well as the GO derivative are able to form consistent, integrated pellets without a binder The nitrogen adsorption isotherms show that the microporous character of all the samples is preserved after the compression, but the porosity decreases significantly Nevertheless, GO has a protective effect against the 25 or 50 bar applied pressure, as 75% of the pore volume and the apparent surface area is saved in HKUST 1@GO, while only 43% and 47%, respectively, in HKUST-1 after compression XRD diffractograms indi cate a certain level of structural damage XRD, nitrogen and methane adsorption data concomitantly imply that the incorporated GO moder ates the effect of the external pressure The flexible GO sheets may act as compressible spacers thus inhibiting amorphisation of the MOF crystals The methane uptake decreases proportionally to the applied pressure, but for HKUST-1@GO the effect is about half as strong: GO enhances the pressure tolerance particularly at the higher compression applied Further experiments are needed to optimize the pelletisation pressure in order to reduce the loss in the methane uptake capacity [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] Funding [19] This research was supported by the OTKA grant K 128410 from National Research, Development and Innovation Office (NKFIH), Hungary and by the BME-Nanotechnology and Materials Science (BME IE-NAT) TKP2020 IE grant [20] CRediT authorship contribution statement [23] ´n: Investigation, (sample preparation, sample char Andrea Doma acterisation, adsorption measurements), Writing - review & editing sz: Investigation, (XRD data, Formal analysis Gyo ă rgy Janos Madara ´fra ´n: Investigation, (TEM imaging) Ying Wang: Writing - review & Sa ´szlo ´ : Conceptualization, Writing editing, commentary Krisztina La review & editing, Resources [24] [21] [22] [25] [26] [27] Declaration of competing interest [28] 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 [29] [30] [31] Acknowledgments [32] The authors are grateful to Prof K Kaneko for fruitful discussions We also extend our warm thanks to G Bosznai and B Pinke (BME) for their invaluable technical assistance [33] References [35] [34] [36] [1] Z Navas-Anguita, D García-Gusano, D Iribarren, Renew Sustain Energy Rev 112 (2019) 11–26, https://doi.org/10.1016/j.rser.2019.05.041 [2] A Alonso, J.M Vico, A.A Markeb, M Busquets-Fit´ e, D Komilis, V Puntes, A S´ anchez, X Font, Sci Total Environ 595 (2017) 51–62, https://doi.org/ 10.1016/j.scitotenv.2017.03.229 [3] K.V Kumar, K Preuss, M.-M Titirici, F Rodríguez-Reinoso, Chem Rev 117 (2017) 1796–1825, https://doi.org/10.1021/acs.chemrev.6b00505 [4] DoE Technical Targets for Hydrogen Storage Systems for Material Handling Equipment Fuel cell technologies office, Office of energy efficiency & renewable energy, energy.gov, Last time accessed, https://www.energy.gov/eere/fuelcells/d oe-technical-targets-hydrogen-storage-systems-material-handling-equipment, September 2020 [5] The Advanced Research Projects Agency – Energy (ARPA-E) of the U.S department of energy, DE-FOA-0000672: Methane Opportunities for Vehicular Energy (MOVE) (September 2020) FoaIddc1d731e-f2cf-4be9-b6ac-ab315582d000" \o, https://arpa-e-foa.energy.gov/Default.aspx?Search=move&SearchType=", https ://arpa-e-foa.energy.gov/Default.aspx?Search=move&SearchType=, [37] [38] [39] [40] [41] [42] https://arpa-e-foa.energy.gov/Default.aspx?Search=move&SearchType=#Fo aIddc1d731e-f2cf-4be9-b6ac-ab315582d000 Y He, F Chen, B Li, G Qian, W Zhou, B Chen, Coord Chem Rev 373 (2018) 167–198, https://doi.org/10.1016/j.ccr.2017.10.002 C Petit, Curr Opin Chem Eng 20 (2018) 132–142, https://doi.org/10.1016/j coche.2018.04.004 B Wang, L.-H Xie, X Wang, X.-M Liu, J Li, J.R Li, Green Energy & Environ (2018) 191–228, https://doi.org/10.1016/j.gee.2018.03.001 S.S.-Y Chui, S.M.-F Lo, J.P.H Charmant, A.G Orpen, I.D Williams, Science 283 (1999) 1148–1150, https://doi.org/10.1126/science.283.5405.1148 Y Peng, V Krungleviciute, I Eryazici, J.T Hupp, O.K Farha, T Yildirim, J Am, Chem Soc 135 (2013) 11887–11894, https://doi.org/10.1021/ja4045289 T Tian, Z Zeng, D Vulpe, M.E Casco, G Divitini, P.A Midgley, J SilvestreAlbero, J.-C Tan, P.Z Moghadam, D Fairen-Jimenez, Nat Mater 17 (2018) 174–179, https://doi.org/10.1038/nmat5050 N Moitra, S Fukumoto, J Reboul, K Sumida, Y Zhu, K Nakanishi, S Furukawa, S Kitagawa, K Kanamori, Chem Commun 51 (2015) 3511–3514, https://doi.org/ 10.1039/c4cc09694k G.J.H Lim, Y Wu, B.B Shah, J.J Koh, C.K Liu, D Zhao, A.K Cheetham, J Wang, J Ding, ACS Mat, Letture (2019) 147–153, https://doi.org/10.1021/ acsmaterialslett.9b00069 A Ahmed, M Forster, R Clowes, P Myers, H Zhang, Chem Commun 50 (2014) 14314–14316, https://doi.org/10.1039/c4cc06967f K.M Rambau, N.M Musyoka, N Manyala, J Ren, H.W Langmi, Mater Today Proc (2018) 10505 N Balahmar, A.C Mitchell, R Mokaya, Adv Energy mater, 1500867 (2015), https://doi.org/10.1002/aenm.201500867 B Szczesniak, S Borysiuk, J Choma, M Jaroniec, Mater Horizons (2020) 1457–1473, https://doi.org/10.1039/D0MH00081G F.-X Coudert, Chem Mater 27 (2015) 1905–1916, https://doi.org/10.1021/acs chemmater.5b00046 J Liu, Y Wang, A.I Benin, P Jakubczak, R.R Willis, M.D LeVan, Langmuir 26 (17) https://doi.org/10.1021/la102359q, 2010, 14301-14307 M.I Nandasiri, S.R Jambovane, B.P McGrail, H.T Schaef, S.K Nune, Coord Chem 311 (2016) 38–52, https://doi.org/10.1016/j.ccr.2015.12.004 J Kim, S.-H Kim, S.-T Yang, W.-S Ahn, Microporous Mesoporous Mater 161 (2012) 48–55, https://doi.org/10.1016/j.micromeso.2012.05.021 D Bazer-Bachi, L Assi´ e, V Lecocqa, B Harbuzarua, V Falk, Powder Technol 255 (2014) 52–59, https://doi.org/10.1016/j.powtec.2013.09.013 J Dhainaut, C Avci-Camur, J Troyano, A Legrand, J Canivet, I Imaz, D Maspoch, H Reinsch, D Farrusseng, CrystEngComm 19 (2017) 4211–4218, https://doi.org/10.1039/c7ce00338b G.W Peterson, J.B DeCoste, T.G Glover, Y Huang, H Jasuja, K.S Microporous mesoporous mater https://doi.org/10.1016/j.micromeso.2013.02.025, 2013, 179, 48-53 ˜ ez, Nanomaterials 10 (2020) 1089, https://doi.org/ D Ursueguía, E Díaz, S Ord´ on 10.3390/nano10061089 A Terracina, M Todaro, M Mazaj, S Agnello, F.M Gelardi, G Buscarino, G, J Phys Chem C 123 https://doi.org/10.1021/acs.jpcc.8b08846, 2019, 17301741 M Muschi, C Serre, Coord Chem Rev 387 (2019) 262–272, https://doi.org/ 10.1016/j.ccr.2019.02.017 B Szczę´sniak, J Choma, M Jaroniec, J Colloid Interface Sci 514 (2018) 801–813, https://doi.org/10.1016/j.jcis.2017.11.049 A Dom´ an, B Nagy, L.P Nichele, D Srank´ o, J Madar´ asz, K L´ aszl´ o, Appl Surf Sci 434 (2018) 1300–1310, https://doi.org/10.1016/j.apsusc.2017.11.251 W Huang, X Zhou, Q Xia, J Peng, H Wang, Z Li, Ind Eng Chem Res 53 (2014) 11176–11184, https://doi.org/10.1021/ie501040s Q Al-Naddaf, M Al-Mansour, H Thakkar, F Rezaei, Ind Eng Chem Res 57 (2018) 17470–17479, https://doi.org/10.1021/acs.iecr.8b03638 J Cort´es-Súarez, V Celis-Arias, H.I Beltr´ an, A Tejeda-Cruz, I.A Ibarra, J E Romero-Ibarra, E S´ anchez-Gonz´ alez, S Loera-Serna, ACS Omega (2019) 5275–5282, https://doi.org/10.1021/acsomega.9b00330 L Ge, L Wang, V Rudolph, Z Zhu, Rsc Adv https://doi.org/10.1039/c3ra44250k, 2013, 3, 25360-25366 F Xu, Y Yu, J Yan, Q Xia, H Wang, J Li, Z Li, Chem Eng J 303 (2016) 231–237, https://doi.org/10.1016/j.cej.2016.05.143] N Justh, B Berke, K L´ aszl´ o, I.M Szil´ agyi, J Therm, Anal Calorim 131 (2018) 2267–2272, https://doi.org/10.1007/s10973-017-6697-2 D.C Marcano, D.V Kosynkin, J.M Berlin, A Sinitskii, Z Sun, A Slesarev, L B Alemany, W Lu, J.M Tour, ACS Nano (2010) 4806–4814, https://doi.org/ 10.1021/nn1006368 A Paudics, S Farah, I Bertoti, K Laszlo, M Mohai, A Szilagyi, M Kubinyi, Appl Surf Sci., 541, 2021, p 148541, https://doi.org/10.1016/j.apsusc.2020.148451 (in press) F Wang, H Guo, Y Chai, Y Li, C Liu, Microporous Mesoporous Mater 173 (2013) 181–188, https://doi.org/10.1016/j.micromeso.2013.02.023 A Dom´ an, J Madar´ asz, K L´ aszl´ o, Thermochim Acta 647 (2017) 62–69, https:// doi.org/10.1016/j.tca.2016.11.013 A Dom´ an, Sz Kl´ebert, J Madar´ asz, Gy S´ afr´ an, Y Wang, K L´ aszl´ o, Nanomaterials 10 (2020) 1182, https://doi.org/10.3390/nano10061182 F.H Allen, Acta cryst B 58 (2002) 380, https://doi.org/10.1107/ S0108768102003890 C.F Macrae, I.J Bruno, J.A Chisholm, P.R Edgington, P McCabe, E Pidcock, L Rodriguez-Monge, R Taylor, W.P.A Jacco van de Streek, J Appl, Cryst 41 (2008) 466–470, https://doi.org/10.1107/S0021889807067908 A Dom´ an et al Microporous and Mesoporous Materials 316 (2021) 110948 [43] S Brunauer, P Emmett, E Teller, J Am, Chem Soc 60 (1938) 309–319, https:// doi.org/10.1021/ja01269a023 [44] M.M Dubinin, L.V Radushkevich, Chem Zentr (1947) 875–890 [45] M Thommes, K Kaneko, A.V Neimark, J.P Olivier, F Rodriguez-Reinoso, J Rouquerol, K.S.W Sing, Pure appl, Inside Chem 87 (2015) 1051–1069, https:// doi.org/10.1515/pac-2014-1117 [46] A Dom´ an, O Czakkel, L Porcar, J Madar´ asz, E Geissler, K L´ aszl´ o, Appl Surf Sci 480 (2019) 138–147, https://doi.org/10.1016/j.apsusc.2019.02.177 [47] F.-X Coudert, Acta Crystallogr B71 (2015) 585–586, https://doi.org/10.1107/ S2052520615020934 [48] J Rouquerol, P Llewellyn, F Rouquerol, Stud Surf Sci Catal 160 (2007) 49–56 ... compounds 3.3 Adsorption of methane The effect of pelletisation on the methane adsorption capacity is of primary importance for gas storage application The methane adsorption performance of the... process is limited to the range 2–5 0 nm Transformation of the primary adsorption data was performed with the Quantachrome ASiQwin software (version 3.0) Water vapour adsorption/ desorption isotherms... uptake seems to be governed by the MOF Graphene oxide (GO) was found to improve the methane adsorption properties of HKUST-1 [30,31] GO is a single or oligo-layer graphene decorated with various oxygen