Nanocrystallization of triazolate-based metal–organic frameworks boosting photocatalytic hydrogen peroxide production

Abstract

Metal–organic frameworks (MOFs) have emerged as a revolutionary platform for photocatalysis owing to their flexible structures, tunable electronic properties and high density of active sites. However, the bulk crystalline form of MOFs typically suffers from limited light-harvesting capability, low surface accessibility, and sluggish mass transport, which collectively restrict their photocatalytic activity and durability. Herein, we report a novel, aqueous-stable Cd(II)-based coordination framework, [Cd(C₆N₆O₂)(H₂O)₂], assembled from conjugated bistriazole-p-benzoquinone (BTBQ) ligands. Moreover, downsizing Cd-BTBQ crystals (Cd-BTBQ-C) into nanocrystals (Cd-BTBQ-N) effectively increased the density of accessible active sites, shortened charge transport pathways and improved light-harvesting efficiency. As a result, Cd-BTBQ-N exhibited a H₂O₂ production rate of 1.18 mmol g⁻¹ h⁻¹ under visible light in pure water, which was a 7.0-fold enhancement over the bulk Cd-BTBQ-C. Notably, Cd-BTBQ-N delivered a production rate of 10.99 mmol g⁻¹ h⁻¹ in the presence of ethanol and maintained high activity under continuous-flow conditions, demonstrating superior performance compared to previously reported MOF-based photocatalysts. Comprehensive characterization revealed that Cd-BTBQ-N followed a dual-channel reaction mechanism involving the synergistic action of both water oxidation and oxygen reduction pathways, in contrast to the single pathway observed in the bulk crystalline samples. This work not only elucidated the structure-dependent reaction mechanism in MOF photocatalysts but also highlighted nanocrystallization as a promising strategy for developing highly performance MOF-based photocatalytic systems.