Photocatalytic membranes based on Cu–NH₂-MIL-125(Ti) protected by poly(vinylidene fluoride) for high and stable hydrogen production

A porous, photocatalytically active, and water-stable composite membrane has been developed based on Cu-NH₂-MIL-125(Ti), a titanium-based metal-organic framework (MOF) and PVDF polymeric matrix. To tune the structural and functional properties of the PVDF/MOF composites, the loading degree of the MOF within the polymer was systematically varied. The most effective performance of the composite material was achieved with a 10% wt/wt loading of MOF into the PVDF matrix. Analysis of the photoactivity under UV-vis revealed that increasing the MOF content from 1 to 10% led to an improvement in the H₂ production rate from 86.0 to 389.1 μmol h^-1 m^-2 and from 55.5 to 466.0 μmol h^-1 m^-2 for water-based and AcN-based electrolytes, respectively. Furthermore, the stability of the MOF is significantly improved when incorporated into the PVDF matrix, maintaining its structural integrity even after 20 h of the photoprocess. The SEM images and EDX mapping successfully validate the presence of the MOF within the PVDF matrix following the photoprocess. The study outlines the experimental procedures for synthesizing Cu-NH₂-MIL-125(Ti), preparing PVDF composites, and details on the photocatalytic experiments. The practical application of our approach can be further expanded to enhance the photocatalytic performance of PVDF-protected unstable MOFs.