Herein, environmentally benign chitin nanofiber (ChNF) membranes were fabricated by regulating suspension behavior. The introduction of zeolitic imidazole frameworks (ZIF-8) into the composite membranes led to the domain formation of ChNF derived by coordinative interaction, resulting in pore size-tunable membranes.
Carbohydrate Polymers 275 (2022) 118754 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Research paper Pore-size control of chitin nanofibrous composite membrane using metal-organic frameworks Younghan Song a, b, 1, Jin Young Seo a, c, 1, Hyungsup Kim b, Sangho Cho a, d, *, Kyung-Youl Baek a, d, e, * a Materials Architecting Research Center, Korea Institute of Science Technology, Seoul 02792, Republic of Korea Department of Organic and Nano System Engineering, Konkuk University, Seoul 05029, Republic of Korea Department of Chemical and Biological Engineering, Korea University, 5-1 Anam-dong, Seongbuk-gu, Seoul 136-713, Republic of Korea d Division of Nano & Information Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Republic of Korea e KHU-KIST Department of Converging Science and Technology, Kyung Hee University, Seoul 02447, Republic of Korea b c A R T I C L E I N F O A B S T R A C T Keywords: Chitin nanofiber (ChNF) Pore size control Bioderived membrane Water purification Rheology Herein, environmentally benign chitin nanofiber (ChNF) membranes were fabricated by regulating suspension behavior The introduction of zeolitic imidazole frameworks (ZIF-8) into the composite membranes led to the domain formation of ChNF derived by coordinative interaction, resulting in pore size-tunable membranes Based on the rheological, morphological, and structural characterizations, the driving force of pore-size control was studied in the aqueous suspension of ChNF and ZIF-8 according to the relative concentration At critical con centration, the 30-ChNF membrane presents superior water permeance (40 LMH h− 1) while maintaining a high rejection rate (>80% for all organic dyes) Moreover, the molecular size cut-off of the composite membranes for dyes can be controlled in the range of less than nm to nm The experimental results provide a simple strategy for the preparation of pore tunable ChNF membranes using MOF with high mechanical strength, good durability, high flux, dye rejection, and antifouling ability Introduction In general, nanofibers are defined as fibers with diameters less than 100 nm with a high aspect ratio of more than 100 (Xia et al., 2003; Li & Xia, 2004) Material-wisely, nanofibers are interesting nanomaterials due to their unique features from dimensional, optical, and mechanical characteristics (Lee, An, Kim, Yoon, & Yarin, 2018; Venkatesan et al., 2020) Therefore, nanofibers have been gained great attention for a wide range of application areas such as nanocomposites, filtrations, energy storage, catalyst, and biomedical fields (Cui et al., 2020; Maity & Mandal, 2018; Seo, Cho, Lee, Lee, & Baek, 2020;) Most of all, the nanofibrous structure has been widely utilized in membrane technology for purifying wastewater as an energy-saving process (Subrahmanya et al., 2021) Among various pollutants in wastewater, organic dyes have raised great concerns due to their enormous usage, and lethality Not only are the dyes toxic and carcinogenic, but even small amounts can inhibit sunlight transmission, leading to metabolic imbalances (Moradi & Sharma, 2021; Rajabi, Mahanpoor, & Moradi, 2017; Robati et al., 2016; Zhu, Chen, & Lou, 2012) As an effective way to remove dyes, the nanofibrous membrane presents high performances due to the threedimensional inter-connected pore structure (Wu et al., 2015) This nanofibrous membrane was produced from a polymer solution by electrospinning and could be controlled by their diameters or mor phologies with rheological tuning, voltage, and so on (Chronakis, 2005) However, the electrospinning process requires a large amount of organic solvents with low productivity, causing environmental pollution With increasing environmental concerns, nanofibers from the hier archical structures of biomass have been greatly gained attention by their environmental friendliness In nature, many types of biomasses have nanofibers in their complex hierarchical organization such as cel lulose, chitin, etc (Chen et al., 2010; Xu, Mao, Peng, Luo, & Chang, 2018) These nanofibers can be extracted in physical or chemical ways (Isogai, Saito, & Fukuzumi, 2011; Rossi et al., 2021) This has triggered many researchers to explore the application of membrane technology using biomass-driven nanofibers The hydrophilicity of biomass-driven nanofibers can give an advantage for improving the membrane * Corresponding authors at: Materials Architecting Research Center, Korea Institute of Science Technology, Seoul 02792, Republic of Korea E-mail addresses: scho@kist.re.kr (S Cho), baek@kist.re.kr (K.-Y Baek) These authors contributed equally https://doi.org/10.1016/j.carbpol.2021.118754 Received 17 August 2021; Received in revised form 23 September 2021; Accepted October 2021 Available online 16 October 2021 0144-8617/© 2021 The Authors Published by Elsevier Ltd This is an open (http://creativecommons.org/licenses/by-nc-nd/4.0/) access article under the CC BY-NC-ND license Y Song et al Carbohydrate Polymers 275 (2022) 118754 properties of anti-fouling ability and high wettability (Ma et al., 2014; Lotfikatouli et al., 2021) Also, the biomass-driven nanofibrous mem brane can be prepared by water with the wet-laid process, so-called nanopaper fabrication (Yoon, Doh, & Im, 2011) During the wet-laid process, the pore structure of the nanofibrous membrane can be blocked by a random distribution of the fibers, resulting in a highly dense nanopaper (Fukuzumi, Saito, Iwata, Kumamoto, & Isogai, 2009; Kim, Choi, & Jin, 2020) To avoid blocking the pore, the biomass-driven nanofibrous membrane was prepared at the thin thickness with the support membrane This thin layer membrane with nanofibers showed high water permanence with a high rejection rate (Zhang, Deng, Soyekwo, Liu, & Zhu, 2016) Still, there are challenging issues on the durability and pore-structure control of the membrane The pore-size modulation of the nanofibril-based membrane from biomass is highly required to broaden its applications: for example, hemofiltration of blood for medical care, purification of industrial wastewater, and seawater desalination (Shin et al., 2019; Soyekwo et al., 2017) So far, three different approaches were conducted for pore modulation First, the fabrication of nanofibrous membranes with smaller diameters induces dense packing of nanofiber, resulting in pore size decrement (Zhao, Zhou, & Yue, 2000) Second, the membrane morphology with a thinner active layer can induce opening interconnected pore structure, leads to increment of pore size (Chen, Duan, Shi, & Fang, 2017) For instance, Buehler and coworkers (Ling, Jin, Kaplan, & Buehler, 2016) demonstrated the control of membrane pore size by varying active layer thickness (