Bimetallic MnZn-MOF-74 with enhanced percentage of MnIII: Efficiently catalytic activity for direct oxidative carboxylation of olefins to cyclic carbonates under mild and solvent-free condition

• Published in: Journal of colloid and interface science 2024-10, Vol.671, p.232-247
• Main Authors: Gao, Ziyu, Wang, Huidong, Hu, Yuchen, Sun, Jianmin
• Format: Article
• Language: English
• Subjects: Bimetallic MnZn-MOF-74; carbon dioxide; carboxylation; catalysts; catalytic activity; Lewis acids; Lewis bases; Multiple active sites; olefin; oxidants; Oxidative carboxylation of olefins; Solvent-free condition; Tandem reaction
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2024.05.104

Bimetallic Mn99.3Zn0.7-MOF-74 with the highest ratio of MnIII exhibited efficient performance for the direct oxidative carboxylation of olefins to cyclic carbonates under mild and solvent-free conditions using aqueous TBHP oxidant, and could be reused for 5 consecutive runs without significant loss in activity and structure. [Display omitted] •In the obtained bimetallic MnZn-MOF-74, the valance state distributions of Mn were regulated with different Zn amount.•High ratio of active MnIII as main oxidant centers and Lewis acid/base sites made Mn99.3Zn0.7-MOF-74 catalyst efficient.•On direct oxidative carboxylation of styrene, Mn99.3Zn0.7-MOF-74 provided 92% styrene conversion with 59.8% selectivity.•Mn99.3Zn0.7-MOF-74 presented great universality to various olefins substrates and could be reused consecutively 5 runs. Multi-functional MOF catalyst with oxidative- and acid- centers showed potential in olefins oxidative carboxylation to cyclic carbonates directly. In this work, a series of bimetallic MnZn-MOF-74 with different molar ratios of Mn and Zn were synthesized successfully through a one-pot facile method. Thoroughly characterization indicated that the existence of Zn regulated the valance state distribution of Mn in the obtained MnZn-MOF-74. Mn99.3Zn0.7-MOF-74 with the highest ratio of MnIII (61.3 %) performed the most efficient activity for olefin direct tandem oxidative carboxylation reaction using aqueous tert-butyl hydroperoxide oxidant under solvent-free condition of 90 °C, 1.0 MPa CO2 and 4 h. Mn99.3Zn0.7-MOF-74 also showed satisfactory versatility and recyclability. Based on the experiments, a feasible mechanism was presented. Thanks to the high ratio of active MnIII as main oxidative center, the coordination unsaturated bimetal Mn and Zn as Lewis-acid sites, O2– of metal − O as Lewis-base sites and combined effect with Bu4NBr cocatalyst, Mn99.3Zn0.7-MOF-74 presented efficient performance for the direct synthesis of cyclic carbonates from olefins. The metal Zn in MOF can regulate the valance state distribution of Mn and result in efficient catalytic property, presenting a potential avenue for direct oxidative carboxylation reaction of olefins to cyclic carbonates synthesis.