Mixed-linker strategy for suppressing structural flexibility of MOF membranes for gas separation

Abstract Structural flexibility is a critical issue that limits the applications of MOF membranes for gas separation. Herein we propose a mixed-linker approach to suppress the structural flexibility of the CAU-10-based membranes. Specifically, pure CAU-10-PDC membrane is of high separation performance but at the same time highly unstable for the separation of CO 2 /CH 4 . A partial substitution (30 mol.%) of the linker PDC with BDC significantly improves its stability. Such an approach also allows for the aperture size of MOFs. The optimized CAU-10-PDC-H (70/30) membrane possesses a high separation performance for CO 2 /CH 4 (separation factor of 76 and CO 2 permeability of 1,111 Barrer under 2 bar of feed pressure at 35 ℃). A combination of in situ characterization with XRD and DRIFT spectroscopy, as well as DFT calculations, unveils the origin of the mixed-linker approach to enhancing the structural stability of the mixed-linker CAU-10-based membranes during the gas permeation tests.