Non-covalent polyhedral oligomeric silsesquioxane-polyoxometalates as inorganic–organic–inorganic hybrid materials for visible-light photocatalytic splitting of water

A new series of visible light responsive and water-stable inorganic-organic-inorganic hybrid materials such as polyoxometalate (POM) and polyhedral oligomeric silsesquioxanes (POSS) with different metals was prepared, and these materials include {[PW12O40][(NH3CH2CH2CH2)(Bu-i)(7)Si8O12](3) (POM(W)-POSS), [PMo12O40][(NH3CH2CH2CH2)(Bu-i)(7)Si8O12](3) (POM(Mo)-POSS) and [PMo10V2O40][(NH3CH2CH2CH2)(Bu-i)(7)Si8O12](5) (POM(MoV)-POSS)}; these materials containing a cationic electron donor of amino-substituted POSS (POSS-NH2) on an anionic electron acceptor of POM have been developed for efficient and sustainable photocatalytic H-2 production. It is interesting to note that the synthesized hybrid materials exhibit remarkable photocatalytic H-2 production activities under visible-light irradiation. The maximum H-2 production rate of 485 mol h(-1) g(-1) is achieved using POM with heterometallic sites, i.e., (MoV)-POSS rather than that having homometallic sites. The enhanced photocatalytic H-2 production is mainly due to improved charge carrier separation by electron-deficient metal sites and a red shift in the absorption, as revealed from photoluminescence and UV-vis spectra. Importantly, POM-POSS hybrid materials demonstrate excellent water stability during photocatalysis due to the hydrophobicity of the hybrid materials, which results from the integration of hydrophobic POSS-NH2 with POMs in contrast to free POMs. Additionally, the successful integration of POSS-NH2 into POMs is confirmed using FT-IR, NMR, ESI mass spectroscopy, and elemental and thermogravimetric analyses. The present study may open new possibilities in the design and development of stable POM organic/inorganic hybrid materials for solar energy conversion applications.