Spatial functionality gradient in a ZIF-8 thin film membrane

a vapor-phase process applied to a ZIF-8 monolithic film. Anisotropic diffusion of a reactive linker-imidazole-2-carboxaldehyde (CHO-Im)-into the ZIF-8 monolith results in a gradient incorporation of CHO-Im, yielding a ZIF-8-CHO monolith. Spatial anisotropy of the CHO functional groups is confirmed through X-ray diffraction, scanning electron microscopy, and vibrational spectroscopy. To demonstrate its potential, we fabricated an anodic aluminium oxide-supported membrane and highlighted its enhanced gas permselectivity compared to pristine membranes.