2-Methylimidazole Modified Co-BTC MOF as an Efficient Catalyst for Chemical Fixation of Carbon Dioxide

[(CH 3 ) 2 NH 2 ][Co 3 (BTC)(HCOO) 4 (H 2 O)]·H 2 O (Co-BTC) was synthesized under solvothermal conditions, further used as the precursor for the synthesis of 2-methylimidazole modified Co-BTC (2MeIm@Co-BTC- x ). The characteristics of 2MeIm@Co-BTC- x were systematically characterized by various technologies including XRD, FESEM, FT-IR, XPS, N 2 -adsorption, TG-DTG and CO 2 /NH 3 -TPD. It was found that except for the crystal faces (0 1 1) and (− 1 0 2) corresponding to ZIF-67 and Co-BTC, a new crystal phase appeared at 12.22 o for the modified Co-BTC, which may be attributed to the coordination between 2MeIm and unsaturated Co ions of Co-BTC. Interestingly, a new structure of hexagonal prisms together with hierarchical porous were also formed for the modified Co-BTC. Besides, when this composite was explored as a heterogeneous catalyst for catalytic conversion of carbon dioxide with epichlorohydrin (ECH) as probe, an obvious enhancement in catalytic activity was obtained compared with the fresh Co-BTC, suggesting that 2MeIm ligands within the modified Co-BTC played a great role on the coupling process. Furthermore, 97.21% of ECH conversion and 98.79% of chloropropene carbonate selectivity were gained over 2MeIm@Co-BTC-1.0 under optimal conditions (3.0 MPa, 90 °C, 5 h, 0.75 wt% catalyst of ECH). Additionally, only a slight decrease in catalytic activity was found after the optimal sample was reused three times. Finally, a mechanism for interpreting the coupling process of carbon dioxide cycloaddition with epoxide was proposed. Graphic Abstract One-pot catalytic conversion of CO2 into cyclic carbonate over 2-methylimidazole modified Co-BTC