π-conjugated chromophore functionalized high-nuclearity titanium-oxo clusters containing structural unit of anatase for photocatalytic selective oxidation of sulfides

N-doping has significant influence in manipulating the properties of TiO_(2),and this has stimulated the development of N-donor-functionalized titanium-oxo clusters(TOCs)as molecular models to study the structure-property relationship.However,the structural type and photoresponsive application are still limited for such TOCs,especially regarding the high-nuclearity TOCs that contain structure unit of TiO_(2)for photocatalysis.Herein,we showed the synthesis of a series of high-nuclearity TOCs 1-3 compounds usingπ-conjugated 1,10-phenanthroline(phen)as chromophore and N-donor functional ligand.Compound 1 features cocrystal structure composed of one[Ti_(26)]~(2+)and half[Ti_(22)]~(2+),which renders it as the first cocrystallized TOC containing two positively charged species and phen-functionalized TOC showing the highest nuclearity up to 37 Ti centers.By adjusting the synthetic conditions,the individual{Ti_(22)}and{Ti_(26)}clusters can also be isolated as Compounds 2 and 3,respectively.The core structure of{Ti_(22)}is mainly constructed from four lacunary{Ti_(4)}derived from pentagonal{Ti(Ti)_5}unit,while{Ti_(26)}is built from four complete{Ti(Ti)_5}unit.Notably,a{Ti_8O_(14)}structure unit of anatase TiO_(2)can be identified in{Ti_(26)}.Based on the unique structural features and proper photophysical and photochemical properties of Compounds 1-3,they are applied for photocatalytic sulfoxidation.Owing to the presence of anatase structure unit in{Ti_(26)}and the synergistic effect from{Ti_(22)}and{Ti_(26)},the catalytic performance presents in the order of Compound 1>Compound 3>Compound 2.This work provides excellent models to understand the structureproperty relationship from the perspective of cocrystallization and Ti-O binding model and will further promote the application of TOCs as functional catalysts for organic transformation.

Polyoxovanadate-based metal-organic frameworks consisted of open vanadium sites for selective catalytic oxidation of sulfides

Three novel polyoxovanadate-based metal-organic frameworks(POV-MOFs),[Co_(2)(1,4-dtzb)_(3)]{V_(4)O_(12)}(V-Co-MOF_(1),1,4-dtzb=1,4-di(4H-1,2,4-triazol-4-yl)benzene],[Co_(3)(1,3-dtzb)_(2)][{V_(6)O_(18)}(V-Co-MOF_(2),1,3-dtzb=1,3-di(4H-1,2,4-triazol-4-yl)benzene],[Co_(4)(4,4’-bdtzb)_(2)]{V_(8)O_(24)}(V-Co-MOF_(3),4,4’-bdtzb=4,4’-(1,1’-biphenyl)-4,4’-diylbis(4H-1,2,4-triazole)benzene]were facilely synthesized and structurally characterized.Single-crystal X-ray diffraction analysis indicates that all the POV-MOFs possess open V sites lined on POV clusters of{V_(4)O_(12)}/{V_(6)O_(18)}/{V_(8)O_(24)}that uniformly distribute on the robust three-dimensional frameworks.This unique structural feature allows them to show high performance for sulfidesulfoxide transformation when performing the reaction in MeOH at 50℃ for 45 min using H_(2)O_(2) as green oxidant.Notably,V-Co-MOF1 exhibited the highest catalytic efficiency,with a conversion>99% and selectivity up to 97% for a series of sulfide substrates.Control reaction demonstrated the catalytically active centers are the open V sites while the MOF skeleton constructed from Co^(2+)and ligands also contributes to enhance the conversion and selectivity via synergistic effect.Furthermore,V-Co-MOF1 can be used as a stable heterogeneous catalyst,and both the structural integrity and catalytic performance were well reserved after five cycles,demonstrating their great potential for advanced catalytic oxidation.