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. (C) 2019 Elsevier Inc. All rights reserved.