Multicomponent metal-organic frameworks (MC-MOFs) are constructed from multiple (≥ 3) metals and/or ligands and often exhibit dramatically increased structural complexity compared to their 2 component (1 metal, 1 linker) counterparts. The resulting structural features of MC-MOFs, such as multiple chemically unique pore environments and a plurality of diverse molecular diffusion pathways, can be advantageous for gas separation applications. Here, we report two isoreticular multicomponent MOFs, bMOF-200 (4 components; Cu, Zn, adeninate, pyrazolate) and bMOF-201 (3 components; Zn, adeninate, pyrazolate). Both MOFs contain 3 unique pore environments interconnected by distinct pore window shapes and sizes. We use Kohn-Sham density functional theory (DFT) along with the climbing image nudged elastic band (CI-NEB) method to predict potential H₂/CO₂separation ability of bMOF-200. We examine the H₂/CO₂ separation performance of bMOF-200 using both column breakthrough and membrane permeation studies, where membranes exhibit a H₂/CO₂separation factor of 7.9. Although topologically identical, the pore space of bMOF-201 is significantly different than bMOF-200 and one molecular diffusion pathway is occluded by coordinating charge-balancing formate and acetate anions. A consequence of this structural difference is reduced permeability to both H₂ and CO₂and a significantly improved H₂/CO₂ separation factor of 22.2 compared to bMOF-200, which makes bMOF-201 membranes competitive with some of the best performing MOF membranes in terms of H₂/CO₂separations.

Gotz Veser

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