Electron Injection from Photoexcited Metal–Organic Framework Ligands to Ru₂ Secondary Building Units for Visible-Light-Driven Hydrogen Evolution

We report the design of two new metal–organic frameworks (MOFs), Ru-TBP and Ru-TBP-Zn, based on Ru2 secondary building units (SBUs) and porphyrin-derived tetracarboxylate ligands. The proximity of Ru2 SBUs to porphyrin ligands (∼1.1 nm) facilitates multielectron transfer from excited porphyrins to Ru2 SBUs to enable efficient visible-light-driven hydrogen evolution reaction (HER) in neutral water. Photophysical and electrochemical studies revealed oxidative quenching of excited porphyrin by Ru2 SBUs as the initial step of the HER process and the energetics of key intermediates in the catalytic cycle. Our work provides a new strategy to building multifunctional MOFs with synergistic ligands and SBUs for efficient photocatalysis.本研究报道了两种新型金属有机框架（metal–organic frameworks, MOFs）Ru-TBP与Ru-TBP-Zn的设计，该类框架基于Ru2次级结构单元（secondary building units, SBUs）与卟啉衍生四羧酸盐配体构建。Ru2次级结构单元与卟啉配体的间距约为1.1 nm，这一近距离特性可促进激发态卟啉向Ru2次级结构单元发生多电子转移，从而在中性水中实现高效的可见光驱动析氢反应（visible-light-driven hydrogen evolution reaction, HER）。光物理与电化学研究表明，HER过程的初始步骤为Ru2次级结构单元对激发态卟啉的氧化淬灭，同时该研究还阐明了催化循环中关键中间体的能级情况。本工作为构建具备协同配体与次级结构单元的多功能金属有机框架以实现高效光催化提供了全新策略。