Synthesis,Assembly And Property Study Of High-Nuclearity Molybdenum Oxide Clusters

High-nuclearity molybdenum oxide clusters remain an important member of polyoxometalate family,which possess clear structures and composition,adjustable sizes and excellent redox activity,had been widely used in catalysis,medicine,energy materials,etc.Rational design and assembly of building units is an effective strategy to build high-nuclearity molybdenum oxide clusters.The classical building blocks of high-nuclearity molybdenum oxide clusters are pentagon{Mo₈}units and{Mo₂}and{Mo₁}units,using these building blocks to give rise to new functional high-nuclear molybdenum oxide clusters can not only enrich the high-nuclearity metal-oxygen cluster family,but also help to fundamentally understand the relationship between structure and function of polyoxometalates.Based on this point,four high-nuclearity molybdenum oxide clusters were prepared under hydrothermal condition,including capped wheel{Mo₁₃₂}featuring a rare quasi-isomerism with known{Mo₁₃₂}ball,high-nuclearity molybdenum oxide clusters{Mo₇₂M₃₀}(M=Mo^V,V^IV)isostructural balls and half-closed product{Ce₁₁Mo₉₆}based on molecular tailoring strategy.The synthesis,structures and assembly rules of these high-nuclearity molybdenum oxide clusters had been studied in detail,moreover,their photochemistry,proton conduction and dye adsorption properties had also been investigated.The main contents are shown as follows:1.A capped wheel{Mo₁₃₂}featuring a rare quasi-isomerism with known{Mo₁₃₂}ball had been successfully designed and obtained under hydrothermal condition,namely Na₂₂H₃₀{Mo₁₃₂O₃₇₂（OH）₁₀（H₂O）₁₂（SO₄）₅（CH₃COO）₂₀}·122H₂O.Both{Mo₁₃₂}clusters possess identical reduction degree(45%,Mo₆₀^VMo₇₂^VI)and characteristic{（Mo）Mo₅}motifs with similar connection rules.This pair of‘molybdenum framework isomer’exhibits disparate optical behaviors,at this level,capped wheel{Mo₁₃₂}is an unprecedented member of‘Mo Green’family after the classical wheel-shaped‘Mo Blue’family.In addition,both spherical and capped wheel{Mo₁₃₂}quasi-isomers exhibit good proton conduction performance under different temperature and relative humidity conditions.This work lays the foundation for the design and synthesis of functional isomers based on polyoxometalate clusters.2.Isostructural{Mo₇₂M₃₀}(M=Mo^V,V^IV)were successfully obtained under hydrothermalcondition,namely Na₆[{(Mo^VI)Mo₅^VIO₂₁（H₂O）₃（SO₄）}₁₂{（Mo^VO）₃₀（H₂O）₂₀}]·72H₂O≡{Mo₁₀₂}and Na₃₆[{(Mo^VI)Mo_I5^VO₂₁（H₂O）₃（SO₄）}₁₂{(V^IVO)₃₀（H₂O）₂₀}]·112H₂O≡{Mo₇₂V₃₀},which belong to spherical high-nuclearity molybdenum oxide cluster family.They are ideal molecular isostructural models for exploring dye adsorption studies.The results show that{Mo₇₂V₃₀}with more negative charge has a better dye adsorption performance for the cationic dye MB⁺.Meanwhile,the adsorption performance of{Mo₇₂V₃₀}based on different sizes,charges and mixed dyes had also been systematically discussed.The design and synthesis of isostructural{Mo₇₂M₃₀}(M=Mo^V,V^IV)with dye adsorption properties provides new ideas for exploring the assembly and function of other isostructural high-nuclearity molybdenum oxide clusters.3.We have report the first case of Ce-mediated molecular tailoring strategy from parent{Mo₁₃₂}capped wheel to specific product{Ce₁₁Mo₉₆}in giant polyoxometalate assemblies,namely Na₃H₆{Ce₁₁Mo₉₆O₂₈₆（H₂O）₁₀₁（SO₄）₈}·94H₂O.Experiencing an‘Inner-On-Outer’binding process with the substituent of{Mo₂}reactive sites in{Mo₁₃₂},the site-specific Ce ions drive the dissociation of{Mo₂^*}clipping sites and finally give rise to a predictable half-closed product{Ce₁₁Mo₉₆}.By virtue of the tailor-made open cavity,the{Ce₁₁Mo₉₆}achieves high proton conduction,nearly two orders of magnitude than that of{Mo₁₃₂}capped wheel.This work offers a significant step toward the controllable assembly of polyoxometalate clusters through a Ce-mediated molecular tailoring process for desirable properties.