Photocatalytic dehydrogenative C(sp³)–C(sp³) homocoupling over an electrostatically self-assembled MoS₂/CdS heterojunction

Photocatalytic dehydrogenative homocoupling of benzyl derivatives is a green and sustainable strategy for the direct construction of C(sp³)–C(sp³) bonds. However, the efficiency of these reactions is significantly hindered by the poor surface kinetics of the hydrogen evolution reaction (HER) and severe charge recombination. Herein, we demonstrate that the electrostatic self-assembly of MoS₂ colloids on CdS nanosheets (MoS₂/CdS) can efficiently capture photogenerated electrons to drive H⁺ reduction, owing to their intrinsic excellent catalytic ability for HER and their strong electron-sink effect for charge separation. This, in turn, facilitates the migration of photogenerated holes from the bulk to the surface, enabling more holes to initiate the oxidative cleavage of C–H bonds in benzyl derivatives, such as cumene. More importantly, MoS₂ colloids, with Mo atoms sandwiched between two sulfur layers, exhibit much lower interaction with produced ·C(CH₃)₂Ph radicals compared to conventional HER cocatalysts, such as noble or transition metal co-catalysts. This facilitates the departure of the ·C(CH₃)₂Ph radicals for C(sp³)–C(sp³) homocoupling reactions, thus enhancing selectivity toward bicummyl. This work presents an efficient, green, and cost-effective strategy for the dehydrogenative homocoupling of benzyl derivatives to construct C(sp³)–C(sp³) bonds under mild conditions.