Abundant Carbohydrates as Sustainable Catalysts for CO₂–Epoxide Coupling toward Cyclic Carbonates

Cyclic carbonates are valuable products obtained through CO₂ insertion into epoxides, but this transformation requires catalytic activation because of the high thermodynamic stability of CO₂. This work investigates abundant, low-cost carbohydrates as sustainable catalysts in combination with tetrabutylammonium salts under solvent-free conditions. Nanocrystalline cellulose and analytical- or commercial-grade sucrose were evaluated in reactions with styrene oxide at 1 or 10 bar of CO₂. Conversion and selectivity were determined by ¹H NMR spectroscopy. Commercial sucrose significantly improved epoxide conversion under all tested conditions, increasing it from 24% to 64% at 1 bar and 60 °C, from 48% to 80% at 10 bar and 100 °C with 0.1 mol% TBABr, and from 60% to 99% with 1 mol% TBABr. Nanocrystalline cellulose increased conversion from 11% to 81% when combined with TBAI. These results demonstrate a strong synergistic effect between carbohydrates and tetrabutylammonium salts.