Hierarchically porous covalent organic framework-based hybrid membrane for efficient toluene/N2 separation

Covalent organic framework (COF)-based hybrid membranes have emerged as promising candidates for volatile organic compounds (VOCs) recovery. However, hybrid membranes with both high selectivity and permeability remain to be explored. Herein, a hierarchically structured COF (HCOF) with combined micro-, meso- and macropore was synthesized by Triformylphloroglucinol (Tp) and 2,5-diaminobenzoic acid (Pa-COOH) via NaCl templating, and subsequently employed as fillers to fabricate COF-based hybrid membranes. The abundant mesopores and macropores in HCOF provided fast mass transfer channels with reduced mass transfer resistance toward aromatics, thus enhancing the diffusion of VOCs in the hybrid membranes and exhibiting higher permeability. The optimal membrane with 2 wt% HCOF demonstrates a remarkable toluene permeability of 1.4 × 10 −6  mol μm m −2 s −1  Pa −1 along with a high toluene/N 2 selectivity of 589. The design of the hierarchical pore COF-based hybrid membrane in this study may inspire the development of advanced membrane structures for VOCs recovery.