Mixed matrix membranes incorporated with size-reduced Cu-BTC for improved gas separation

Metal-organic frameworks (MOFs), with large surface area and selective gas adsorption capability, can be the promising additives in mixed matrix membranes (MMMs) for potential gas separation. In this study, mixed matrix membranes with dispersed Cu-BTC [Cu₃(BTC)₂] have been fabricated and employed for gas separation. The sonication treatment was adopted to reduce the crystal size of MOFs and improve their affinity to the polymer matrix. The crystal structure, surface area and gas adsorption properties of as-synthesized and sonication-treated Cu-BTC were measured and compared. The morphology of the derived mixed matrix membranes varied with sonication intensity and Cu-BTC particle size, and the elimination of interfacial voids indicated the improvement of the adhesion between Cu-BTC crystals and the polymer matrix. The permeation test revealed that the gas permeance and selectivity of membranes depend on the crystal size of Cu-BTC fillers. Incorporation of the sonicated Cu-BTC results in enhancing both gas permeability and selectivity of the derived mixed matrix membranes. The analysis of permeation and gas sorption results also indicates that MOFs improve both diffusivity and solubility of gas molecules thus enhancing the permeability and selectivity of the membrane.