Continuous UiO-66-Type Metal-Organic Framework Thin Film on Polymeric Support for Organic Solvent Nanofiltration

For the first time, continuous polycrystalline UiO-66-NH₂ thin film supported by a cross-linked Matrimid substrate was successfully fabricated via in situ solvothermal synthesis at room temperature for organic solvent nanofiltration. The integrated structure of the formed UiO-66-NH₂ selective layer was inferred by various characterizations including X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. We have demonstrated that pretreatment of the substrate by an organic ligand, the number of solvothermal synthesis cycles, and the reaction time play important roles in MOF film formation. The newly developed UiO-66-NH₂ membrane possesses high surface hydrophobicity and mean pore size of 0.89 nm in diameter. It shows an exceptional rejection of 96.33% to Rose Bengal with moderate ethanol permeance of 0.88 L m^-2 h^-1 bar^-1. Benefiting from the extraordinary chemical stability of Zr-MOF crystals, the UiO-66-NH₂ membrane shows excellent stability in different solvents, implying their great potential for real applications. This work provides useful insights into the fabrication of continuous UiO-66-type MOF membranes on polymeric substrates, which are very promising in practical separations involving organic solvents.