Two 3D Two-Fold Interpenetrated Dia-Like Polyoxometalate-Based Metal-Organic Frameworks: Synthesis and Sulfide Selective Oxidation Activity

Two novel polyoxometalate (POM)-basedcomplexes constructedfrom rigid triazole ligands have been hydrothermally synthesized andstructurally characterized. The catalytic conversion of sulfide wasstudied in detail. It is noteworthy that complexes 1 and 2, as heterogeneous catalysts, show high activity and selectivityto sulfoxide in the oxidation reaction, accompanied by the advantagesof steady reuse and easy recovery. Two new three-dimensional (3D) polyoxometalate-basedmetal-organicframeworks (POMOFs), [M-2(btap)(4)(H2O)(4)(HPMo10 (VI) Mo-2 O-V(40))] (M = Co (1) and Cd (2); btap = 3, 5-bis(1 & PRIME;, 2 & PRIME;, 4 & PRIME;-triazol-1 & PRIME;-yl)pyridine),have been synthesized under mild hydrothermal conditions and characterizedin detail. Single-crystal X-ray diffraction (SXRD) analysis indicatesthat 1 and 2 are isostructural. In complexes 1 and 2, the metal ion is coordinated with theligand to form two different left and right helical one-dimensionalchains, which are alternately connected in a twisted form to builda two-fold interpenetrated three-dimensional structure, and the polyoxometalateis encapsulated into in the pores generated by the interpenetratingstructure. It is noteworthy that 1 and 2, as recyclable catalysts, possess favorable heterogeneous catalyticactivity and excellent sulfoxide selectivity in sulfide oxidationreactions, with H2O2 as an oxidant. By reasonof the high dispersion of polyoxometalate with good intrinsic activityin the skeleton structure, the title complex has high activity. Inaddition, no obvious decrease of sulfoxide yield is observed afterat least five cycles. These results indicate the excellent catalyticactivity and sustainability of 1 and 2.