Multifunctional approach to improve water oxidation performance with MOF-based photoelectrodes

•Promising PEC water oxidation with MOF-based photoactive electrodes was achieved.•A dual strategy was employed to simultaneously enhance charge separation and catalytic activity in MIL-125-NH2 and UIO-66-NH2 MOF photoelectrodes.•Providing a selective contact for electrons and an efficient co-catalytic component resulted in the enhancement of the photocurrent by a factor 26.•This dual strategy opens new avenues for the application of MOFs in photoelectrochemistry and photocatalysis. [Display omitted] Metal-Organic Frameworks (MOFs) are a group of compounds with high porosity and diverse capabilities in photoelectrochemistry. The use of these compounds as photocatalysts and photoelectrodes is still a strong challenge due to bulk and surface recombination issues. To solve this problem, we applied a dual strategy to simultaneously enhance charge separation and catalytic activity in MIL-125-NH2 and UIO-66-NH2 MOF photocatalysts. Mesoporous TiO2 was used as electron-selective contact on the MOF surface (MOF/TiO2) to minimize bulk recombination. On the other hand, to increase the MOF catalytic activity for water oxidation, a well-matched Co3(PO4)2 (CoPi) co-catalyst (CoPi/MOF/TiO2) was used. The obtained results showed that CoPi and TiO2 were introduced in the MOF structure. The (CoPi/MOF/TiO2) photoelectrodes showed a photocurrent density 26 times higher compared to the reference MOF at 1.23 V vs. RHE for PEC water oxidation of artificial seawater, validating the developed strategy for further photocatalytic and photoelectrochemical applications.