A Bipyridyl Covalent Organic Framework with Coordinated Cu(I) for Membrane C3H6/C3H8 Separation

Abstract Covalent organic frameworks (COFs) mixed matrix membranes (MMMs) combining individual attributes of COFs and polymers are promising for gas separation. However, applying COF MMMs for propylene/propane (C 3 H 6 /C 3 H 8 ) separation remains a big challenge due to COF inert pores and C 3 H 6 /C 3 H 8 similar molecular sizes. Herein, the designed synthesis of a Cu(I) coordinated COF for membrane C 3 H 6 /C 3 H 8 separation is reported. A platform COF is synthesized from 5,5′‐diamino‐2,2′‐bipyridine and 2‐hydroxybenzene‐1,3,5‐tricarbaldehyde. This COF possesses a porous 2D structure with high crystallinity. Cu(I) is coordinated to bipyridyl moieties in the COF framework, acting as recognizable sites for C 3 H 6 gas, as shown by the adsorption measurements. Cu(I) COF is blended with 6FDA‐DAM polymer to yield MMMs. This COF MMM exhibits selective and permeable separation of C 3 H 6 from C 3 H 8 (C 3 H 6 permeability of 44.7 barrer, C 3 H 6 /C 3 H 8 selectivity of 28.1). The high porosity and Cu(I) species contribute to the great improvement of separation performance by virtue of 2.3‐fold increase in permeability and 2.2‐fold increase in selectivity compared to pure 6FDA‐DAM. The superior performance to those of most relevant reported MMMs demonstrates that the Cu(I) coordinated COF is an excellent candidate material for C 3 H 6 separation membranes.