Post-synthetic modification of highly stable UiO-66-NH2 membranes on porous ceramic tubes with enhanced H2 separation

Due to their rationally controlled pore size and easy functionalization, metal-organic frameworks (MOFs) are a promising candidate for membrane separation. As one of the most stable MOFs, UiO-66 has attracted intense attention for the preparation of molecular sieving membranes. A new post-synthesis modification (PSM) strategy was developed to enhance the separation selectivity of supported UiO-66-NH2 membranes on porous ceramic tubes called UiO-66-NH2@SA by using salicylaldehyde (SA) modification. The mixed gas separation factors of H-2/CO2 and H-2/CH4 can be improved due to constrictions of the pore size through reaction of -NH2 with SA giving iminophenol moieties. Notably, SA-modified UiO-66-NH2 membranes are rather stable, at a high operation temperature of 200 degrees C and 1 bar, mixture separation factors of 11.3 for H-2/CO2 and 22 for H-2/CH4 can be obtained. Further, no obvious performance degradation has been observed after 3 months storing in air. This high stability of UiO-66-NH2@SA membrane could provide possibility for the industrial applications of hydrogen separation and purification.