Dual-Layer MOF Composite Membranes with Tuned Interface Interaction for Postcombustion Carbon Dioxide Separation

Abstract

Summary Metal-organic frameworks (MOFs) have immense potential as sorbents and inorganic membranes for CO2 separation. However, the trade-off between selectivity and adsorption capacity or permeability remains a challenge. Here, we present the fabrication of MOF core-shell particles and dual-layer membranes that show enhanced CO2/N2 separation performance compared with individual MOF materials. A highly selective MOF layer with narrow pore size is grown on the surface of a highly permeable MOF layer with large pore size. Chemical binding at the interface between the two MOFs makes it possible to form a continuous defect-free shell layer on the surface of the core or base layer. The two dual-layer MOF@MOF membranes, SIFSIX-3-Ni@SIFSIX-1-Cu and SIFSIX-3-Ni@HKUST-1, represent the first examples of pure inorganic membranes constructed from different MOFs with lattice mismatch. The CO2/N2 selectivity of the HKUST-1 and SIFSIX-1-Cu membranes is improved from 5.7 to 13.4 and 2.3 to 7.4, respectively, after the growth of a selective layer of SIFSIX-3-Ni.