Design,Synthesis And Property Study Of New Crystalline Materials Based On Molybdenum Oxide Clusters

Crystalline materials based on molybdenum oxide clusters possess clear and abundant compositions and structures,tunable size and excellent redox properties,which show broad application prospects in the field of catalysis,material,and medicine etc.Building block assembly strategy is an effective method to build crystalline materials based on molybdenum oxide clusters.However,the reported building blocks based on molybdenum oxide clusters are mainly focus on classical pentagons-containing{Mo（Mo）₅}units,simple{Mo₂}and{Mo₁}units.Exploring the assembly process of novel building blocks based on molybdenum oxide clusters is expected to achieve the preparation of crystalline materials based on molybdenum oxide clusters with diverse structures and properties.Herein,crystalline materials based on molybdenum oxide clusters featuring novel building blocks,including highly reduced polyoxometalate{Mo₇₄},organotin-stabilized fully reduced polyoxometalate{Mo₁₉^VSn₁₂}as well as Mo-based metal-organic molecular cages{Mo₁₂^V（BTC）₁₂}and{Mo₁₂^V/VI（BTC）₈},were successfully obtained by introducing anionic templates,organotin groups or carboxyl ligands into the design and synthesis of crystalline materials based on molybdenum oxide clusters.The synthesis,structure and assembly rules for above crystalline materials based on molybdenum oxide clusters had been systematically discussed,their proton conduction and dye adsorption properties had also been well investigated.1.Ahighlyreducedmolybdenumoxidecluster（C₂H₈N）₁₄（NH₄）₄H₁₄[Mo₄₈^VMo₂₆^VIO₂₀₂（OH）₁₂（SO₄）₆]·46H₂O({Mo₇₄},65%reduction degree),was successfully synthesized through the building block strategy.{Mo₇₄}can be described as two{Mo₃₄}trimers connected by six symmetrically distributed{Mo O₄}tetrahedra.Each trimer consists of one fully reduced{Mo₆^V},three partially reduced{Mo₄^V/VI}and{Mo₅^V/VI}secondary building blocks,which are guided by MO₄(M=S⁶⁺or Mo⁶⁺)anion templates.The proton conductivity study shows that{Mo₇₄}exhibits a high proton conductivity of 1.32×10^-2 S cm^-1 at 55℃and 90%relative humidity,the proton conductivity activation energy is estimated to 0.31 e V based on the Arrhenius equation,indicating the Grotthuss mechanism.This work provides a basis for the preparation of highly reduced polyoxometalate clusters through building block strategy.2.Anorganotin-stabilizedfullyreducedpolyoxometalate（NH₄）₁₅[Sn₃^IV（CH₃）₃（OH）₃O]₄[Mo₁₉^V（OH）₂O₆₂]·39H₂O({Mo₁₉^VSn₁₂})was successfully obtained by introducing organotin into the polyoxomolybdate systems.{Mo₁₉^VSn₁₂}can be described as four disordered tetra-coordinated Mo centers encapsulated into a truncated tetrahedron{Mo₁₈^V}cage,which is further stabilized by four triangular{Sn₃}units,thus the whole cluster presents a“octahedral-octahedral-tetrahedral”assembly mode.Meantime,the stability in air and photochemical properties of this fully reduced polyoxometalate were investigated.In addition,the proton conductivity shows that{Mo₁₉^VSn₁₂}exhibits a proton conductivity of 2.41×10^-3 S cm^-1 at 50℃and 95%relative humidity,the proton conduction follows the vehicle mechanism and the activation energy is 0.51 e V.3.Two Mo-based metal organic molecular cages（H₂NEt₂）₂₄[（Mo₂^VO₄）₆（BTC）₁₂]·2DEF({Mo₁₂^V（BTC）₁₂})and TBA₂（H₂NMe₂）₁₈[（Mo₂^VO₆）₂(Mo₂^VIO₅)₄（BTC）₈]({Mo₁₂^V/VI（BTC）₈}),were successfully prepared under solvothermal conditions.{Mo₁₂^V（BTC）₁₂}is composed with six corner-sharing{Mo₂^VO₄}secondary building units and twelve BTC ligands,while{Mo₁₂^V/VI（BTC）₈}is composed with six edge-sharing（{Mo₂^VO₆}）and corner-sharing({Mo₂^VIO₅})secondary building units based on dinuclear molybdenum oxide clusters and eight BTC ligands.The dye adsorption experiments show that{Mo₁₂^V/VI（BTC）₈}displays better cationic dye adsorption performance.