The photocatalytic activity for CO reduction of a series of Ni-substituted polyoxometalates (POMs) differing in nuclearity, shape and size, has been investigated under visible light irradiation, with [Ru(bpy)] (bpy = 2,2′-bipyridine) as photosensitizer and triethanolamine as sacrificial donor. The tetrabutylammonium salt of the tetranuclear species was found to exhibit the highest CO production and its stability under photocatalytic conditions was demonstrated. The catalytic performance was significantly lower for the alkaline salt due to the separation of the POM from its counter-ions occurring only for the tetrabutylammonium salt. Photophysical experiments evidenced a bimolecular electron transfer from the reduced photosensitizer [Ru(bpy)] to the POM, the former arising from the reductive quenching of the [Ru(bpy)] excited state by triethanolamine. This was further supported by DFT calculations, which also showed that the POM accumulates at least two electrons and four protons to carry out the CO reduction catalytic process.

中文翻译：

---

Ni取代的多金属氧酸盐光催化CO2还原：结构-活性关系和机理见解

在可见光照射下，研究了一系列不同核、形状和尺寸的镍取代多金属氧酸盐 (POM) 的 CO 还原光催化活性，[Ru(bpy)] (bpy = 2,2′-联吡啶)作为光敏剂和三乙醇胺作为牺牲供体。发现四核物质的四丁基铵盐表现出最高的 CO 产量，并证明了其在光催化条件下的稳定性。碱性盐的催化性能明显较低，因为仅四丁基铵盐才会发生 POM 与其抗衡离子的分离。光物理实验证明了从还原光敏剂[Ru(bpy)]到POM的双分子电子转移，前者是由三乙醇胺对[Ru(bpy)]激发态的还原猝灭引起的。 DFT计算进一步支持了这一点，该计算还表明POM积累了至少两个电子和四个质子来进行CO还原催化过程。