Pore Engineering of Covalently Connected Metal-Organic Framework Nanoparticle-Mixed-Matrix Membrane Composites for Molecular Separation

Fine-tuning and pore environment control of covalently connected metal-organic framework (MOF) and mixed-matrix membrane (MMM) composite materials were achieved. Core-shell-type, dual-functionalized, zirconium-based MOFs were prepared through a postsynthetic ligand exchange (PSE) process, and active vinyl functionalities on the surface of MOF nanoparticles were utilized for polymerization by forming interfacial-covalent connections between MOF nanoparticles and polymeric membranes via thiol-ene click photopolymerization. The target functionality of the MOF pore originated from the parent MOFs, allowing pore engineering of the MOF-MMM composite materials. A series of defect-free, interface-controlled, and core-functionalized MOF-MMMs were prepared through the present methodology, and the NO2-functionalized/covalently connected MOF-MMM showed the highest CO2 permeability and solubility without loss of selectivity. This facile and versatile approach will be useful for the fabrication of functional MOF nanoparticle-based membranes for various applications, such as catalysis and separation.