Large-scale screening of covalent organic framework/polymer Mixed-matrix membranes for advanced gas separations

Abstract

Mixed matrix membranes (MMMs) that incorporate covalent organic frameworks (COFs) as fillers in polymers offer a promising route to overcome the permeability‐selectivity trade‐off of polymeric membranes. However, the enormous chemical diversity of COFs has limited the large‐scale evaluation of COF/polymer MMMs. In this work, we performed a large‐scale computational screening using molecular simulations to compute CO 2 , CH 4 , N 2 , H 2 , and O 2 permeabilities of COFs to evaluate 971 642 COF/polymer MMMs for CO 2 /CH 4 and O 2 /N 2 separations, and 694 030 COF/polymer MMMs for CO 2 /N 2 and H 2 /CO 2 separations. Incorporation of COFs enhanced polymers’ gas permeability, with increases of up to 75%, 74%, and 74% for CO 2 , H 2 , and O 2 , and MMMs achieved maximum CO 2 , H 2 , and O 2 permeabilities of 9.1 × 10 4 , 3.3 × 10 4 , and 1.8 × 10 4 Barrer, respectively. Comparison with metal‐organic framework (MOF)/polymer MMMs constructed from the same polymer set revealed that COF‐based MMMs improve gas permeabilities, whereas MOF‐based MMMs achieve higher selectivities, particularly for H 2 /CO 2 separation. Analysis of the top‐performing COF fillers using the molecular fingerprint method revealed that nitrogen‐rich heterocyclic motifs, pore size distribution, and pore uniformity play key roles in determining gas permeation behavior. Overall, our work established structure‐performance relationships for COF/polymer MMMs and provides molecular‐level design guidelines for developing next‐generation polymeric gas separation membranes.