Visible‐Light‐Driven Photocatalytic Methanol Activation on Hexagonal CdS for Triggering C–H Methylation

Light‐driven methanol activation paves the way for pursuing C–H methylation of N‐heteroarenes, where selectively converting methanol into the corresponding hydroxymethyl radical (•CH2OH) is an essential prerequisite. Inspired by the versatile methanol activation on photoexcited solids, we here report a practicable semiconductor‐based photocatalytic system for C–H methylation of N‐heteroarenes. To be specific, hexagonal cadmium sulfide (h‐CdS) was identified to be an ideal platform for visible‐light‐driven photocatalytic methanol activation, where selective •CH2OH generation undergoing a hole‐transfer process without any additional co‐catalysts or co‐solvent could trigger C–H hydroxymethylation of N‐heteroarenes. The following electron transfer between photoexcited h‐CdS and hydroxymethylated intermediates could finally lead to the formation of methylated N‐heteroarenes. The transformations facilitate the cascade utilization of photoinduced hole and electron, thereby endowing h‐CdS with extraordinary photocatalytic performance. Besides, selective generation of hydroxymethylated/methylated product could be facilely implemented in the presence/absence of electron scavengers.