| As a molecular model of nano Ti O2,titanium-oxide clusters（TOCs）,which possess accurate structures and excellent stability,have been widely used in photocatalysis,photoluminescence and photoelectric sensing properties.With the continuous development of the synthesis method and performance of TOCs,the construction of functional new TOCs has become an important research topic.Up to now,the design and synthesis of TOCs based on pentagonal{Ti（Ti5）}units and new heteroatom-containing TOCs are still in the primary stage.The introduction of new building units and heteroanion templates may help to enrich the structural diversity and functional characteristics of TOCs.Based on this point,a series of novel TOCs were prepared through solvothermal synthesis,including{Ti21}based on pentagonal{Ti（Ti5）}units,ferrocene-functionalized TOCs{Ti6-Fcdc}/{Ti6},and sandwich-type TOC{P8Ti26}constructed based on{PTi12}with heteroatom phosphate-centeredα-Keggin structures.The synthesis,crystal structure and assembly of the above-mentioned TOCs had been studied in detail,and their applications in the fields of photocatalytic water splitting hydrogen production and proton conduction had also been investigated.The detailed contents are shown as follows:（1）A new TOC[（CH3）2NH2]2[Ti21O29（Oi Pr）12（DMF）6（SO4）8]({Ti21})based on pentagonal{Ti（Ti5）}units was successfully prepared by solvothermal synthesis.The secondary building blocks of{Ti21},including‘fused’dimer{Ti11}and the trimer{Ti12}subunits,were based on the pentagonal{Ti（Ti5）}units with unique bonding patterns.The stability in air,solvent tolerance as well as photochemical activity of{Ti21}had been well demonstrated.As an atomic-precise TOCs-based semiconductor photocatalyst,the photocatalytic hydrogen production rate of{Ti21}under UV/Vis light was 191.94μmol/g/h.The presence of pentagonal{Ti（Ti5）}units in{Ti21}contribute an important impact on the regulation of cluster structure and the improvement of photochemical activity.This work provides significant idea for the synthesis of novel TOCs based on pentagonal{Ti（Ti5）}building units.（2）Using ferrocenecarboxylic acid as an organic functional ligand,[Ti6（μ3-O）6（Oi Pr）6（O2CFc）6]({Ti6-Fcdc},Fcdc=ferrocenecarboxylic acid]was successfully synthesized.In contrast,another TOC(C5H12N)2[Ti6O4（Oi Pr）10（O3P-Phen）2（SO4）2]（{Ti6}）was constructed with phenylphosphonic acid and sulfuric acid as inorganic ligands.Both compounds were constructed from two{Ti3}units,showing good solvent tolerance and photochemical activity.Photocatalytic hydrogen production experiments showed that the hydrogen production of{Ti6-Fcdc}within 6 h was as high as 374.24μmol/g,which was about5 times that of{Ti6}.The introduction of ferrocene functional ligand extends the light absorption range of compound to the visible light region,which effectively improves visible light absorption and the efficiency of charge transfer.This work provides an experimental basis for the synthesis of TOCs-based photocatalysts with efficient charge transfer efficiency.（3）Heteroatom-containing TOCs constructed fromα-Keggin{PTi12}was prepared by solvothermal synthesis,namely H2[Ti2（PO4）2（i Pr PO4）4][Ti12O15（PO4）（Oi Pr）12]2（NO3）2·2H2O({P8Ti26}).{P8Ti26}is composed of two{PTi12}units and a central{Ti2（PO4）2（i Pr PO4）4}unit,presenting a rare sandwich-type TOC with phosphate as heteroanion templates.P element in{P8Ti26}had been identified by crystallographic structure,elemental analysis,infrared spectroscopy（IR）,X-ray photoelectron spectroscopy（XPS）,and elemental mapping.Proton conduction experiments showed that the proton conductivity of{P8Ti26}was 1.32×10-4 S·cm-1at 95%RH and 65°C,which is better than some metal-oxygen-cluster-based proton conduction crystalline materials.Its proton conduction possesses the activation energy of 0.36e V based on the Arrhenius equation,indicating the Grotthuss mechanism.The successful synthesis of{P8Ti26}exploits new ideas for the structural design of heteroatom-containing TOCs. |
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