Ionic Liquid-Decorated MIL-101(Cr) via Covalent and Coordination Bonds for Efficient Solvent-Free CO2 Conversion and CO2 Capture at Low Pressure

An imidazolium-based ionic liquid was embedded into MIL-101(Cr) via coordinate and covalent bonds to synthesize heterogeneous catalysts for efficient CO2 capture at low pressure and CO2 fixation with epoxides. In MIL-IL(A), the ionic liquid was coordinated to Cr centers, while in MIL-IL(B), the ionic liquid was attached to MIL-101(Cr) via a covalent bond. These two materials were used for CO2 capture at p/p0 = 0.033 and 0 °C. The results showed that the CO2 absorbing capacity for MIL-IL(A) and MIL-IL(B) is 5.46 and 7.84 times higher than that of the parent MOF, respectively. The ionic liquid loading was measured by IC, CHN, and thermogravimetric analysis (TGA). Furthermore, the catalytic activity of both catalysts was checked in the cycloaddition of CO2 to epoxides in the absence of any cocatalyst and under solvent-free conditions. A firm bond between the ionic liquid and the framework in MIL-IL(B) made it a recyclable heterogeneous catalyst for CO2 fixation with epoxides. The analytical techniques confirmed the grafting of ionic liquid on the MOF structure, and the framework remained intact after 5 cycles in the cycloaddition of CO2 to styrene epoxide.