A 3D POM-Based Supramolecular Framework Hosting a Hexahedral Cage via Hydrogen Bonds for Room-Temperature Oxidative Desulfurization

Abstract

To address the environmental challenges posed by sulfur-containing emissions, the development of efficient catalysts for oxidative desulfurization is highly desirable. Herein, a new [β-Mo8O26]4–-based Co-complex, {[Co(4-pbba)(H2O)5]2(β-Mo8O26)(4-pbba)}·6H2O (Mo8-pbba-Co, 4-H2pbbaBr2 = 1,1′-(1,4-phenylene-bis(methylene))-bis (pyridine-4-carboxylic-acid)dibromo), was obtained by a hydrothermal reaction of Na2MoO4·2H2O, Co(OAc)2·4H2O and 4-H2pbbaBr2. Mo8-pbba-Co represents the first 6-connected 3D polyoxometalate (POM)-based supramolecular framework constructed from [Co(4-pbba)(H2O)5] units and [β-Mo8O26]4– clusters, featuring unique centrosymmetric hexahedral cage-like units {O2(OW)6} formed via hydrogen-bonding interactions. Mo8-pbba-Co exhibits remarkable catalytic activity for oxidative desulfurization at room temperature using H2O2 as an oxidant, achieving 99% conversion and 99% selectivity for CEES in just 6 min, and 98% conversion and 97% selectivity for MPS within 45 min. Mechanistic investigations elucidate a synergistic catalytic effect between the [β-Mo8O26]4– cluster and Co2+ sites, where hydroxyl radicals (•OH) are identified as the key reactive oxygen species. Furthermore, Mo8-pbba-Co demonstrates outstanding recyclability, offering a promising pathway for the development of efficient desulfurization catalysts under mild conditions.