Coordination tailoring of Cu single sites on C₃N₄ realizes selective CO₂ hydrogenation at low temperature

CO₂ hydrogenation has attracted great attention, yet the quest for highly-efficient catalysts is driven by the current disadvantages of poor activity, low selectivity, and ambiguous structure-performance relationship. We demonstrate here that C₃N₄-supported Cu single atom catalysts with tailored coordination structures, namely, Cu-N₄ and Cu-N₃, can serve as highly selective and active catalysts for CO₂ hydrogenation at low temperature. The modulation of the coordination structure of Cu single atom is readily realized by simply altering the treatment parameters. Further investigations reveal that Cu-N₄ favors CO₂ hydrogenation to form CH₃OH via the formate pathway, while Cu-N₃ tends to catalyze CO₂ hydrogenation to produce CO via the reverse water-gas-shift (RWGS) pathway. Significantly, the CH₃OH productivity and selectivity reach 4.2 mmol g^-1 h^-1 and 95.5%, respectively, for Cu-N₄ single atom catalyst. We anticipate this work will promote the fundamental researches on the structure-performance relationship of catalysts.