An unlocked core–shell Cu2O/NiCu-MOF ternary heterojunction on g-C3N4 enables highly efficient photocatalytic reduction of CO2 under visible light

To achieve the "carbon neutrality" goal, a core-crust-based Cu2O/NiCu-MOF and graphite carbon–nitrogen (g-C3N4) strongly coupled ternary photocatalyst (BMCN/300) was prepared by using a simple low-temperature annealing induction effect and heterojunction interface engineering strategy. The BMCN/300 efficiently converts CO2 to CH4 (165.3 μmol h−1 g−1) and CO (51.3 μmol h−1 g−1) under simulated sunlight in the gas–solid mode without additional sacrifice agents and photosensitizer. The experimental and theoretical calculation results indicate that the annealing treatment achieves strong coupling between g-C3N4 and Cu2O/NiCu-MOF, promotes the migration of interface electrons to Cu2O/NiCu-MOF catalytic unit, NiCu sites are heat-activated to an electron-rich state under annealing induction, and Cu2O becomes a high density of photo-excited electron accepting catalyst sites. The strong coupling of Cu2O/NiCu is conducive to the formation of the key intermediate *CHO, thus achieving highly selective photocatalytic CO2 reduction to CH4.