Synergistic Hydrogen‐Bonding and CO 2 Activation: A Sustainable Metal, Halogen, and Solvent‐Free Strategy for CO 2 Cycloaddition

Abstract Conventional catalytic methodologies for the cycloaddition of CO 2 into epoxides predominantly rely on transition metal‐based catalysts in conjunction with detrimental halide‐containing cocatalysts. Thus, developing metal and halide‐free catalysts that function under ambient conditions is highly desirable. The current research endeavours to synthesize a pyrimidine‐based bifunctional organocatalyst via a facile one‐step Schiff‐base condensation reaction. The synthesized organocatalyst efficiently transforms a wide range of epoxides (35 different epoxides, including 6 challenging internal epoxides) into cyclic carbonates with a minimal catalyst loading of just 0.1 mol% under mild conditions (60 °C–100 °C, atmospheric CO 2 pressure) without solvents and cocatalysts. Comprehensive experimental investigations elucidate how the catalyst facilitates the reaction, emphasizing the intricate interplay of hydrogen (H) bonding, spatial arrangement, and catalyst‐substrate interactions. The meticulous analysis, using advanced spectroscopic techniques and density functional theory (DFT) calculations, reveals that hydroxyl groups play a pivotal role in epoxide activation through H‐bonding interactions, whereas the imine nitrogen facilitates CO 2 activation through the formation of a carbamate intermediate. These two interactions collectively accelerate the overall catalytic process. Furthermore, the catalyst exhibits remarkable recyclability over six consecutive catalytic cycles. Therefore, this study underscores the potential of rationally designed metal‐free catalysts in advancing sustainable catalysis through carbon capture and utilization technologies.