Constructing Molecular Junctions with High-Spin Metal Sites in POMOFs to Trigger Heteropoly Blue States for Photocatalytic H<sub>2</sub> Production
Weize Sun, Bo Zhao, Carlos J. Gómez‐García, Haijun Pang, Zhongling Lang, Huiyuan Ma, Xinming Wang, Guixin Yang, Chi‐Ming Au, Wing‐Yiu Yu
Abstract
The spin state of metal atoms may play a key role in the photocatalytic hydrogen evolution reaction (HER) of polyoxometalate (POM)-based catalysts. Herein, we construct two POM-based metal–organic frameworks (POMOFs) with molecular junction structures by integrating a metal–organic framework structure including high-spin state active Co or Ni sites with [GeW 12 O 40 ] 4– (GeW 12 ) POM. These structures have a fast electron transfer channel, in which the electronic structures of the high-spin metal centers may determine whether the POM can produce reduced POM (heteropoly blue, HPB), leading to enhanced HER activity. Upon photoexcitation, the Co II high-spin state has a vacant in the t 2g orbital, which transfers electrons through π-orbitals, enhancing the electron transfer rate and promoting the generation of HPB. Thus, Co 6 -GeW 12 POMOF forms HPB species during the photocatalytic process and has a photocatalytic HER activity as high as 13.7 mmol g –1 h –1 . This value is the highest one obtained for any photocatalyst with POM as a photosensitizer.