A Bipyridyl Covalent Organic Framework with Coordinated Cu(I) for Membrane C 3 H 6 /C 3 H 8 Separation.

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.