Design of bifunctional NH₃I-Zn/SBA-15 single-component heterogeneous catalyst for chemical fixation of carbon dioxide to cyclic carbonates

The novel bifunctional Zn/SBA-15 supported ammonium salt (NH₃I-Zn/SBA-15) as single-component heterogeneous catalyst for the coupling of CO₂ with epoxides was developed. FT-IR, XRD, N₂ adsorption/desorption, TEM, XPS techniques were used to determine the morphological structure and physicochemical properties of NH₃I-Zn/SBA-15 sample. The catalyst exhibited exceptionally effective activity with 93% yield and 99% selectivity and a high TOF of 306 h^-1 to propylene carbonate at 130 °C and 3 MPa of CO₂ for 12 h in the absence of cocatalyst and solvent participation. Also the catalytic system was versatile to the cycloadditions of other epoxides with CO₂ under the optimized reaction conditions. Additionally, the catalyst was easily recycled and reused only with slight loss of activity after five recycles. Besides, a possible catalytic mechanism involving cooperative activation of epoxide and ring-opening by one-component and bifunctional catalyst was proposed. The protocol herein provides important insights on design of novel single-component heterogeneous catalysts for CO₂ relevant transformations.