Preparation of ZnO@BD- <i>g</i> -C ₃ N ₄ Nanoplate Catalysts Mediating Green and Efficient CO ₂ –Epoxide Cycloaddition Reactions for the Synthesis of Cyclic Carbonates

Abstract

The production of green and economically attractive cyclic carbonates from CO 2 as an alternative to the highly toxic and expensive method of phosgene gas is a well-established synthetic route in green chemistry. It is also consistent with achieving net-zero emissions and promoting 100% atom economy. This study presents the preparation and characterization of reusable ZnO@BD- g -C 3 N 4 nanoplate catalysts (1–9), which feature abundant active sites and a dynamic oscillating active architecture and demonstrate a catalytic role in enhancing the fixation of CO 2 to cyclic carbonates under ambient pressure conditions. The structure of the most active ZnO@BD- g -C 3 N 4 nanoplate catalyst (1) was characterized by using FTIR spectroscopy, UV–DR spectroscopy, XRD, SEM-EDS, TEM, XPS, and BET techniques. The ZnO@BD- g -C 3 N 4 nanoplate catalyst (1) showed the best catalytic activity with 98% conversion for epichlorohydrin (ECH) and 99% selectivity toward epichlorohydrin carbonate (ECHC) under appropriate conditions (ambient pressure, 100 °C, 4 h) without the need for any solvent. The ZnO@BD- g -C 3 N 4 nanoplate catalyst (1) has been successfully tested with various terminal and internal epoxides under the same reaction conditions. Additionally, the synergic effect of Lewis acidic active centers resulted in an efficiency of over 93% and a selectivity of about 99% without a significant decrease in catalytic activity during five consecutive reaction cycles in the recyclability test for the ZnO@BD- g -C 3 N 4 /PPNCl catalytic system. In addition, kinetic studies of this cycloaddition reaction revealed that the reaction was pseudo-first-order under similar conditions. The rate constant at 100 °C was 0.8684 h 1, and the activation energy was 45.16 ± 2 kJ/mol.

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