Molecular sieve membrane-based separation technology, featured with low energy consumption and small carbon footprint, has attracted much attention in gas separation.
Metal-organic frameworks (MOFs) are promising in gas separation membranes due to their diversified structures, high porosity and tailored functionalities. However, defect-free MOF membrane fabrication still remains challenging.
Recently, a research group led by Prof. YANG Weishen and Dr. PENG Yuan from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has fabricated flexible soft-solid MOF composite membrane on commercial polyvinylidene fluoride (PVDF) substrate.
Within the membrane structure, the quasi-vertically oriented, solid Zn2(Benzimidazolate)4 particles grown on PVDF substrate provided predominant molecular sieving gas entrances while soft polyamide eliminated defects enclosing MOF particles, resulting in better performance in H2/CO2 separation.
This robust defect-free composite membrane exhibited an outstanding anti-swelling capacity in condensable feedstock. It showed superior separation accuracies for large C2H6 and C3H8 exclusions.
Moreover, the researchers prepared the Zn2(Bim)4 composite membrane with ultra-high MOF loading and excellent flexibility. After membrane folding and unfolding at 90° for 50 consecutive times or rolling into a tube with a diameter of 3 mm (the largest bending curvature that MOF membranes can endure), the membrane separation performance remained exactly the same.
Soft-solid Zero Insertion Force(ZIF)-67 and ZIF-8 composite membrane series were also fabricated. Taking advantages of defect elimination, the intrinsic molecular sieving capacities of the MOF particles were given full play.