Two Dawson-type polyoxometalate-based metal coordination polymers as heterogeneous catalysts for desulfurization

Abstract

Two new Dawson-type polyoxometalate-based metal coordination polymers with cobalt/nickel ions and bridging ligands were prepared in a hydrothermal reaction system, and the chemical formulae are [H₂BBPTZ]₂Co(BBPTZ)₂[P₂W₁₈O₆₂]·2H₂O (1) and [(Ni₂(TBTZ)₂(H₂O)₄][H₂P₂W₁₈O₆₂]·17.5H₂O (2) (BBPTZ = 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl, TBTZ = 1,3,5-tris(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethyl benzene) which were characterized using elemental analysis, IR spectroscopy, TG analyses, PXRD and single-crystal X-ray diffraction analyses. Specifically, both compounds are assembled into 1-D chain architectures via the coordination interactions between cobalt/nickel and the ligands. Subsequently, these 1-D chains are interconnected with the aid of polyoxometalates, facilitating their expansion into 2-D layered configurations. Eventually, through a layer-by-layer stacking process, a 3-D supramolecular network system is meticulously constructed. In addition, the oxidative desulfurization performance of these two compounds towards DBT was investigated, with 8-hour conversions of 94.6% for compound 1 and 98.3% for compound 2, respectively.