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

• Various protonated NH2-Zn/SBA-15 were successfully synthesized and structurally characterized.
• NH3I-Zn/SBA-15 showed significant activity for coupling of CO2 with various epoxides.
• The catalytic reaction was performed under co-catalyst-/solvent-free conditions.
• The catalyst was bifunctional, environmentally benign and recyclable.

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.

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