Catalytic conversion of CO2 to propylene carbonate over Pt-decorated Mg-substituted metal organic framework

Abstract

Porous coordination polymers of Mg (II) dihyroxyterephtalate (Mg-MOF-74) at various Ptx loadings (x = 0–10 wt%) were synthesized, characterized and tested for the catalytic cycloaddition reaction between CO2 and propylene oxide (PO). The reaction was studied over a range of temperatures between (100–170 °C), pressures (9.1–19.5 bar) and reaction times (4–15 hours) to produce propylene carbonate (PC). The results show that the Pt loading on the catalyst surface improves the selectivity toward PC in the presence of dimethylformamide (DMF) and dichloromethane (DCM) which serve as solvents and promoters for the reaction. Pt loading is shown to be concomitantly related to the number of uncoordinated MgO defect sites produced during synthesis. As Pt loading increases, the number of uncoordinated MgO sites in the Mg-MOF-74 framework structure also increases. During reaction, PO conversion and PC selectivity were shown to systematically increase with Pt loading and the number of uncoordinated MgO defect sites. A synergistic effect is observed where the combined use of Ptx/Mg-MOF-74, DMF and DCM exhibit performance benefits beyond their use individually. The catalysts we characterized before and after reaction using XRD, EDX, ICP, BET, SEM and TGA. The catalysts show a relatively high stability and reusability as confirmed by reaction studies, XRD and FE-SEM.