Mn-based MOFs as efficient catalysts for catalytic conversion of carbon dioxide into cyclic carbonates and DFT studies.

Graphical abstract Synthesis of cyclic carbonates from CO 2 and epoxides. Highlights • Mn-based MOF including imidazole linker was observed with the highest catalytic activity. • Carbon dioxide can be inserted into various epoxides in the presence of Im-MnF sample. • 94.99% yield of allyl-glycidyl carbonate was obtained under the optimal conditions. • A proposed mechanism was in line with the DFT calculation. Abstract The present work is aimed to investigate the catalytic activities of various Mn-based MOFs for carbon dioxide coupling with epoxides. The metal organic frameworks, [(CH 3 NH 3 ][Mn(COOH) 3 ] (MA-MnF), [(CH 3 CH 2 NH 3 ][Mn(COOH) 3 ] (EA-MnF), and [C 3 H 5 N 2 ][Mn(COOH) 3 ] (Im-MnF) were studied via several characterizations such as XRD, FT-IR, XPS, N 2 -adsorption, TG-DSC, CO 2 -adsorption and NH 3 -TPD. Interestingly, Im-MnF compound was observed to possess the highest catalytic activity among the studied compounds, which is associated not only with the amounts of basic sites, but also related to the nitrogen-containing species. 97.27% conversion of allyl-glycidyl ether (AGE, TOF: 36.78 h−1) and 97.66% selectivity to allyl-glycidyl carbonate (AGC) were obtained under the explored optimized conditions (100 °C, 15 bar, 6 h, 1.0 wt% of AGE). In addition, only a slight downward in catalytic activity was found when the sample was reused twice. Furthermore, coupling reactions of CO 2 with various epoxides were also performed, of which, the yield of the cyclic carbonates followed the order: Epichlorohydrin > Allyl glycidyl ether > Styrene oxide > Cyclohexene oxide > Propylene oxide. Finally, a mechanism was proposed, which is in good agreement with the DFT calculation. [ABSTRACT FROM AUTHOR]