Branched In₂O₃ Mesocrystal of Ordered Architecture Derived from the Oriented Alignment of a Metal–Organic Framework for Accelerated Hydrogen Evolution over In₂O₃–ZnIn₂S₄

It is fascinating yet challenging to assemble anisotropic nanowires into ordered architectures of high complexity and intriguing functions. We exploited a facile strategy involving oriented etching of a metal–organic fragment (MOF) to advance the rational design of highly ordered nanostructures. As a proof of concept, a microscale MIL-68(In) single crystal was etched with a K3[Co(CN)6] solution to give a microtube composed of aligned MIL-68(In) nanorods. Annealing such a MIL-68(In) microtube readily created an unprecedented branched In2O3 mesocrystal by assembly of In2O3 nanorods aligned in order. The derived ordered-In2O3–ZnIn2S4 is more efficient in catalyzing visible-light-driven H2 evolution (8753 μmol h–1 g–1) outperforming the disordered-In2O3–ZnIn2S4 counterpart (2700 μmol h–1 g–1) as well as many other state-of-the-art ZnIn2S4-based photocatalysts. The ordered architecture significantly boosts the short-range electron transfer in an In2O3–ZnIn2S4 heterojunction but has a negligible impact on the long-range electron transfer among In2O3 mesocrystals. The density functional theory (DFT) calculation reveals that the oriented etching is achieved by the selective binding of the [Co(CN)6]3– etchant on the (110) plane of MIL-68(In), which can drag the In atoms out of the framework in order. Our findings could broaden the technical sense toward advanced photocatalyst design and impose scientific impacts on unveiling how ordered photosystems operate.