Cobalt-based metal-organic frameworks promoting magnesium sulfite oxidation with ultrahigh catalytic activity and stability

In wet magnesia desulfurization, the ultrahigh stable catalysis of sulfite oxidation is a crucial step in byproduct reclaimation. In this study, a robust and efficient catalyst, Co-MOF-74(4), was synthesized through a facile solvothermal method with an optimal Co/ligand ratio of 4:1. The oxidation rate of magnesium sulfite catalyzed by Co-MOF-74(4) was >2.6 times higher than that of previously reported cobalt-based heterogeneous catalysts. Crucially, almost no attenuation of the catalytic activity was observed even after three reuse cycles. The properties of Co-MOF-74(4) before and after the reaction were characterized. Density functional theory calculations demonstrate that the unsaturated cobalt site on the open framework of Co-MOF-74(4) provides greater opportunity for active Co to be attacked by sulfite ions, resulting in the ultra-high catalytic activity of Co-MOF-74(4). In contrast to the conventional impregnated catalysts, the robust combination of active cobalt with ligands prohibits its stripping from the surface of Co-MOF-74(4) particles. The bond length, angle and lattice parameters have only slight changes after sulfite adsorption, which supports the stability of the catalyst in the reaction process.