A new boron modified carbon nitride metal-free catalyst for the cycloaddition of CO2 and bisepoxides

The cycloaddition of CO2 and epoxide is regarded as an eco-friendly, sustainable, and promising way to utilize CO2. However, it is crucial to design and prepare efficient and low-cost catalysts for this reaction. Herein, through controlling condensation temperature, a series of boron modified urea-derived g-C3N4 (x-BCN) were prepared. Notably, more edge defect (−NH2/−NH−) formed at low roasting temperatures and both basic and acidic sites increased after introducing B. 0.30-BCN exhibited superior catalytic performance for cycloaddition of CO2 with 1, 4-butanediol diglycidyl ether and 99% cyclic carbonate yield was acquired at 130 ℃, 2.0 MPa after 20 h reacting. Additionally, 0.30-BCN showed outstanding recyclability and substrate adaptability. The synergistic effects of edge defects, rich mesoporous structure and Lewis acid-base sites were conductive to promoting CO2 cycloaddition. Moreover, a possible multi-synergetic mechanism was proposed. An originality option was provided for preparing a simple, eco-friendly, and efficient metal-free catalyst for practical CO2 fixation.