Ultrathin CoB/NC Nanosheets for Efficient Photothermal Catalytic Cycloaddition of Diluted CO₂: Boron Introduction Enhances Adsorption and Activation of CO₂

Photocatalytic conversion of diluted carbon dioxide (CO₂) is highly desired, while it remains a significant challenge due to the high binding affinity and poor activation of CO₂ by the catalysts. To address this issue, the study optimizes the coordination environment of cobalt (Co) sites by doping with boron (B), which exhibits Lewis acid activity, in cobalt boride (CoB) and nitrogen-carbon (NC) assembled into a 2D CoB/NC nanosheet. The obtained CoB/NC-0.3(900,1) photocatalysts exhibit abundant Lewis acid sites, high CO₂ adsorption and activation abilities, and excellent photothermal catalytic activity. Impressively, CoB/NC-0.3(900,1) shows high activity in the cycloaddition reaction of CO₂ with epichlorohydrin, yielding 98% chloropropene carbonate after 3 h under low CO₂ concentrations (Pco₂ = 0.15 bar), which is nine times higher than that of Co/NC, highlighting its potential for practical application. Mechanism studies reveal that CoB/NC-0.3(900,1) easily generates hot electrons upon light irradiation, which similarly promotes the formation of ring-opening intermediates and enhances the activation of epoxides and CO₂. This study not only offers novel perspectives on the synthesis of advanced 2D nanosheet catalysts for photothermal-assisted CO₂ conversion into high-value products but also provides broader insights into the rational design of catalysts for the photocatalytic conversion of diluted CO₂.