Visible-light-driven hydrogen peroxide production from water and dioxygen by perylenetetracarboxylic diimide modified titanium-based metal–organic frameworks

Abstract

Metal–organic frameworks (MOFs) are promising materials for photocatalytic hydrogen peroxide (H₂O₂) production from water (H₂O) and dioxygen (O₂). However, H₂O₂ production from H₂O and O₂ using MOFs has remained challenging due to the fast recombination of photogenerated charges in the MOF matrix. Herein, a heterojunction structure was constructed by modification of an organic semiconductor, perylenetetracarboxylic diimide (PDI), upon a titanium-based MOF (MIL-125-NH₂), forming MIL-125-PDI to promote the separation of photogenerated charges between PDI and MOFs. Photo/electrochemical characterizations confirmed that the constructed heterostructure indeed promoted the separation and transfer of photogenerated charges. As a result, the as-formed MIL-125-PDI displayed a H₂O₂ production rate of 4800 μM g⁻¹ h⁻¹, which was 4.3 times that of the pristine MIL-125-NH₂ under visible-light irradiation (λ > 420 nm). Furthermore, MIL-125-PDI exhibited a better durability compared with MIL-125-NH₂ with noble-metal Pt nanoparticles as co-catalysts. The results of trapping experiments and electron spin resonance (ESR) spectra of active species for H₂O₂ production indicated that a new one-step two-electron process of O₂ reduction to H₂O₂ occurred in MIL-125-PDI, while the original one observed in MIL-125-NH₂ was a two-step one-electron process. This work used MOFs as the main active component in photocatalysts, which opens up the new application of MOFs in photocatalysis and provides an effective strategy to design MOF-based photocatalysts for artificial photosynthesis of clean liquid fuels.