Solvent-Free Crystallization of Zeolitic Imidazolate Framework Membrane via Layer-by-Layer Deposition

Abstract

Searching for sustainable synthesis methods of metal–organic framework (MOF) membranes has received huge attention in both academia and industry. In this contribution, the compact ZIF-8 membrane with excellent gas separation performance was successfully prepared via an environmentally friendly and simple method, in which the artful layer-by-layer deposition approach was used to achieve the solvent-free crystallization of a well-intergrown and defect-free ZIF-8 membrane. The solvent-free process is a simple and generalized method for construction of MOF membranes, which can avoid using solvents and high autogenous pressure and brings great benefits for energy saving, emission reduction, and safety as well as scalable manufacturing. In addition, the solvent-free crystallization of MOF membranes exhibits more unprecedented advantages to fill the common intercrystalline cracks, pinhole defects, and grain boundary defects on the membrane. The resulting thin ZIF-8 membrane exhibited both competitive H2 permeability of 6.7 × 10–7 mol m–2 s–1 Pa–1 and high H2/CO2 selectivity of 12.3, simultaneously, which is one of the best ZIF-8 membranes ever reported.

Synthesis of high-performance polycrystalline metal–organic framework membranes at room temperature in a few minutes

“…Recently, by decoupling the nucleation and the growth stages, the synthesis of submicron pinhole-free ZIF-8 lms has been reported. 15,20,27,[33][34][35][36][37][38][39] The nucleation stage involves the generation and attachment of a high density of ZIF nuclei or seed crystals, for example by surface modications, [40][41][42][43] microwave irradiation, 44,45 electrophoretic deposition, 22,23,46,47 etc. This is followed by the growth of nuclei/seeds to eliminate any intercrystallite gaps.…”

ZIF-67 Membranes Synthesized on α-Al2O3-Plate-Supported Cobalt Nanosheets with Amine Modification for Enhanced H2/CO2 Permselectivity

“…In comparison to inorganic surface modifiers in literature reports including MgO, ZnO, − , Co­(OH) 2 , , and ZnAl-CO 3 LDH, the cobalt carbonate hydroxide nanolayer used in this study could be completely converted. This avoided the blockage of the support channels by the involved inorganic surface modifier.…”

“…At last, gas permeation data of the membranes prepared in this study were compared with those of other MOF membranes reported in the literature (Figure and Tables S1 and S2). − In fact, the inorganic surface modification strategy has a great influence on the performance of MOF membranes. Table S1 shows the single-gas permeation properties of MOF membranes synthesized without inorganic surface modifiers.…”

Metal and Covalent Organic Frameworks for Membrane Applications

“…For example, Kargari and coworkers placed the poly(phenyl sulfone) (PPSU) support at the bottom of a vessel and then soaked alternately with the salt and the organic solutions, the thickness of the ZIF-8 layer can reach about 10 μm per cycle of growth [66]. Very recently, Yang et al obtained a high-quality ZIF-8 membrane ideal for gas separation, using the layer-by-layer deposition approach with the solvent-free crystallisation method followed by the in-situ heat treatment [67]. Tham et al adapted this method for the preparation of a Zn benzene-1,4-dicarboxylic acid (Zn(BDC)) MOF on a chemically modified polyacrylonitrile (PAN) membrane using water as the sole solvent.…”