Porous biochar with a tubular structure for photothermal CO2 cycloaddition: One-step doping versus two-step doping

Solar-powered carbon dioxide (CO 2 ) conversion over biomass derived carbon (BC) has shown great promise for alleviating global warming and producing useful chemicals. However, their lack of active sites, rapid recombination of photogenerated electron-hole pairs, and low CO 2 uptake abilities pose significant challenges for photo-induced catalysis. Here, we report the fine-tuning of active sites of BC via one-step and two-step calcination of corn stalk with a tubular structure. Strikingly, compared with samples prepared by two-step doping strategies, NB-BC synthesized via a one-step doping process harbors much enhanced activity under relatively mild conditions (Xe lamp, 400 mW/cm 2 , 1 bar CO 2 ) with a considerable cyclic carbonate yield of 99%. The high catalytic performance is attributed to the alteration of pore structure, electronic structure, and active sites due to N, B doping. Moreover, this biochar displays excellent recyclability and retains its applicability under simulated flue gas conditions. Various characterizations and control experiments reveal the combination of thermal catalysis and photocatalysis over this N, B co-doped BC catalyst. Our work provides some insights into the effective applications of biochar in the field of CO 2 catalytic conversion.