Synergistic Effects of Poly(ionic liquids)@MOF-808 Nanocomposites for Direct Conversion of Carbon Dioxide into Dimethyl Carbonate.

The direct synthesis of dimethyl carbonate (DMC) from carbon dioxide (CO2) and methanol (CH3OH) represents one of the most attractive strategies in green chemistry, offering 100% atom economy for CO2 utilization. However, this reaction faces significant thermodynamic and kinetic challenges, limiting its practical application. To overcome these barriers, the development of highly efficient catalysts capable of effectively activating the CO2 is essential to achieve industrially viable DMC yields. Herein, a series of poly(ionic liquids) (PILs)@MOF-808 nanocomposites (including poly[AlDBU]Br@MOF-808, poly[AlDBN]Br@MOF-808, and poly[AlTMG]Br@MOF-808) were successfully synthesized via in situ polymerization. These composites integrate Lewis basic N sites, Lewis acidic Zr centers, and nucleophilic Br- within a MOF-808 framework. The nanocomposites were evaluated in a batch autoclave for the direct synthesis of DMC from CO2 and CH3OH. Among them, poly[AlDBU]Br@MOF-808 showed the highest DMC yield. Through systematic optimization of the poly[AlDBU]Br loading and reaction parameters (including temperature, CO2 pressure, and time), a maximum DMC yield of 2.52 mmol·g-1cat was achieved with poly[AlDBU]Br@MOF-808-0.4 at 120 °C under 3 MPa of CO2 for 5 h. Experimental studies and in situ DRIFTS confirmed the synergistic catalytic effect between MOF-808 and the PILs, highlighting their cooperative role in enhancing CO2 activation and DMC formation. The catalytic performance of poly[AlDBU]Br@MOF-808-0.4 is competitive compared to previously reported catalysts. The fundamental understanding of the synergistic effects between MOF-808 and PILs offers groundbreaking insights for CO2 capture and utilization strategies in direct DMC synthesis.