Ultramicroporous Covalent Organic Framework Nanosheets with Functionality Pair for Membrane C 2 H 2 /C 2 H 4 Separation

Abstract Gas separation efficiency of covalent organic framework (COF) membrane can be greatly elevated through precise functionalization. A pair‐functionalized COF membrane of 1,3,5‐triformylphloroglucinol (TP) and isoquinoline‐5,8‐diamine (IQD) monomers in two and three nodes is designed and synthesized. TP‐IQD is crystallized in a two‐dimensional structure with a pore size of 6.5 Å and a surface area of 289 m 2 g −1 . This COF possesses N−O paired groups which cooperatively interact with C 2 H 2 instead of C 2 H 4 . TP‐IQD nanosheets of ≈10 μm in width and ≈4 nm in thickness are prepared by mechanical exfoliation; they are further processed with 6FDA‐ODA polymer into a hybrid membrane. High porosity and functionality pair of TP‐IQD offer the membrane with significantly increased C 2 H 2 permeability and C 2 H 2 /C 2 H 4 selectivity which are 160 % and 430 % higher of pure 6FDA‐ODA. The boosted performance demonstrates high efficiency of the pair‐functionality strategy for the synthesis of separation‐led COFs.