| Hydrogen energy as one clean and pollution-free energy,has the advantages of lightest relative mass,lowest density and the high calorific value of combustion.Therefore,the development of non-noble metal-based materials for solar-driven water splitting represents an ideal way to continuously produce green energy.Among the heterogeneous and homogeneous catalysts,molecular catalysts with definite composition and atomically precise structures have attracted more and more attention as they will aid to understand the origin of catalytic mechanism and further tune the performance at molecular level.Thus,it is of great importance to explore the well-defined and efficient molecular photocatalysts for solar energy conversion and storage.Polyoxometalates?POMs?are a class of atomically precise metal-oxo clusters,which possess multiple redox active metal sites and can maintain structural integrity under photocatalytic conditions.These advantages enable POMs to be used as pure inorganic ligands to construct abundant molecular photocatalysts.In recent years,many beautiful examples of robust and stable POM-based H2 evolution catalysts have been reported including polyoxotungstates,heteropolyniobates,isopolyoxoniobates,and polytantalotungstates.Unfortunately,larger scale of solar energy transformation is limited as most of them only harvest and utilize UV spectrum.The introduction of transition metal?TM?has been demonstrated to be an effective strategy to engineer the electronic structure of POMs and broaden the spectrum absorption,which provide the chance to tune the catalytic performance and realize water splitting to H2 under visible light irradiation.Cu,as one the most abundant elements,has multiple oxidation states(Cu0,CuI,CuII,and CuIII),which may endow copper with various oxidation states in the photocatalytic reactions.However,there is a dearth of copper-based molecular catalysts reported for photocatalytic HER.In order to promote more research on cu-based molecular catalysts in the field of energy conversion,an earth-abundant POM-based copper cluster[Cu5?OH?4?H2O?2(A-?-SiW9O33)2]10–?1?was studied herein for visible-light-driven H2 evolution.For comparison,two POM-based nickel clusters[Ni5?OH?6?H2O?3(SiW9O33)2]12??2?,[Ni4?H2O?2(PW9O34)2]10??3?were also synthesized.In the system of sacrificial electron donor triethanolamine/photosensitizer[Ir?ppy?2?dtbbpy?][PF6]/white LED light,1exhibited a high turnover number?TON?of 718.9,which was higher than that of 2?582.7?and 3?87.0?.To the best our knowledge,1 represents one of the best earthabundant POM-based HER molecular photocatalysts.Multiple experiments?dynamic light scattering?DLS?measurements,catalyst aging experiments,Fourier-transform infrared?FT-IR?spectroscopy and UV-vis spectroscopy,Hg poisoning experiments and catalyst extraction with inductively coupled plasma mass spectrometry?ICP-MS?analysis?collectively confirm the good stability of 1 under turnover conditions.Our work may draw much attention to develop highly efficient copper-based molecular catalysts for photocatalytic reduction reactions in the future. |
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