Synchronous activation for boosting CO2 cycloaddition over the DABCO-derived ionic liquid confined in MIL-101(Cr) nanocages

CO2 fixation into cyclic carbonates provides a feasible way for carbon mitigation and high-value utilization, while the development of heterogeneous catalysts for efficient substrate activation remains challenging. In this study, the [TBCl]Cl@MIL-101(Cr) catalyst with cooperative active sites was fabricated via in-situ encapsulation strategy. By taking series of characterization techniques and theoretical calculation, the confinement of DABCO-derived dicationic ionic liquid within the nanocages of MIL-101(Cr) was testified. The presence of abundant unsaturated metal (Cr3+) sites in the heterogeneous carrier MIL-101(Cr) enabled efficient activation of epoxide molecules. Simultaneously, the micro-mesoporous structure afforded ample space for CO2 enrichment, which was activated by the quaternary N+ from [TBCl]Cl through electrostatic interactions. The introduced Cl- anions as nucleophilic reagent further synergized to initiate the ring-opening process, thereby boosting the cycloaddition reaction. As a result, a chloropropene carbonate (CPC) yield of 95.9% was acquired over the [TBCl]Cl@MIL-101(Cr) at mild conditions (100 °C, 10 bar, 2.0 h, and 4.00 wt% of catalyst). Furthermore, this encapsulation strategy endowed the developed catalyst with better cyclic stability due to the limiting effect imposed on ionic liquid. This work shed light on the rational assembling of IL@MOFs composites and afforded new pathways for designing high-performance catalysts for CO2 conversion.