Substituted Ti(IV) in Ce-UiO-66-NH2 Metal-Organic Frameworks Increases H2 and O2 Evolution under Visible Light

Metal-organic frameworks (MOFs) as photocatalysts have received increasing attention. In this work, a dual metal-substituted UiO-66-NH2 (Ti/Ce-MOF) containing different Ti/Ce mole ratios (x = 0-2.46) has been prepared via post-synthetic exchange between Ce-UiO-66 and TiCl4, followed by amination. The solid had a high surface area (828-937 m2/g) and a large pore volume (0.451-0.507 m3/g). Under visible light, Ti/Ce-MOF showed x-dependent activity for H2O reduction and oxidation on a film electrode, respectively. However, such a change for H2 evolution in a Na2S/Na2SO3 aqueous solution was observed only after CdS loading. In combination with the photoluminescence and band parameters, we propose that the photoactivity of Ti/Ce-MOF for redox reaction is determined by its ability for electron transfer. Furthermore, there is an interfacial electron transfer from Ti/Ce-MOF to CdS and a hole transfer from CdS to Ti/Ce-MOF, respectively, significantly improving the efficiency of charge separation for redox reactions. This work offers a new insight that Ti substitution benefits the performance of Ce-based MOF.

Automated summary

In this work, a dual metal-substituted MOF material with high surface area and large pore volume was synthesized. It showed specific redox activity under visible light and the combination with CdS significantly improved charge separation efficiency. This study provides a new insight that Ti substitution benefits the performance of Ce-based MOF.