摘要
Photocatalytic selective transform native lignin into valuable chemicals is an attractive but challenging task. Herein, we report a mesoporous sulfur-doped carbon nitride (MSCN-0.5) which is prepared by a facile one-step thermal condensation strategy. It is highly active and selective for the cleavage C alpha-C beta bond in beta-O -4 lignin model compound under visible light radiation at room temperature, achieving 99% substrate conversion and 98% C alpha -C beta bond cleavage selectivity. Mechanistic studies revealed that the C beta-H bond of lignin model compounds activated by holes and generate key C beta radical intermediates, further induced the C alpha -C beta bond cleavage by superoxide anion radicals (center dot O-2(-)) to produce aromatic oxy-genates. Waste Camellia oleifera shell (WCOS) was taken as a representative to further understand the reaction mechanisms on native lignin. 33.2 mg of monophenolic compounds (Vanillin accounted for 22% and Syringaldehyde for 34%) can be obtained by each gram of WCOS lignin, which is 2.5 times as that of the pristine carbon nitride. The present work offers useful guidance for designing metal-free heteroge-neous photocatalysts for C alpha -C beta bond cleavage to harvest monophenolic compounds.
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单位南昌航空大学