(CH3)2NH2][M(COOH)3] (M=Mn, Co, Ni, Zn) MOFs as highly efficient catalysts for chemical fixation of CO2 and DFT studies

Abstract

The present work aimed to investigate the differences of metal species of [(CH3)2NH2][M(COOH)3](DMA-MF, M = Mn, Co, Ni, Zn) compounds being applied as highly efficient catalysts for enhancing the cycloaddition of CO2 with epoxides. The properties of the as-prepared compounds were systematically investigated via characterizations such as XRD, FT-IR, Raman, XPS, CO2-adsorption, TG-DTG, and CO2/NH3-TPD. The DMA-MnF sample was observed with the highest catalytic activity among the studied MOFs, of which metal node (served as Lewis acid sites) and DMA+ groups (functionalized as Lewis basic sites) within the DMA-MF play a synergistically catalytic effect on the coupling process. Furthermore, when the coupling reaction was carried out at 120 °C for 6 h in presence of 2.0 wt.% PO catalyst under 2.0 MPa, 99.68% conversion of PO and 98.01% yield of propylene carbonate (PC) were perfectly obtained over DMA-MnF compound. In addition, the CO2 coupling with 1, 2-epoxybutane, allyl-glycidyl ether, epichlorohydrin, and styrene oxide were also accomplished under the same conditions. Finally, the DFT calculation was utilized to reveal the appropriate reaction path.