Highly Selective Hydrogenation of CO₂ to Ethanol via Designed Bifunctional Ir₁-In₂O₃ Single-Atom Catalyst

Recently, CO₂ hydrogenation for the controlled growth of the carbon chain to produce high-value C₂ or C₂₊ products has attracted great interest, where achieving high selectivity for a specific product remains a challenge, especially for ethanol. Herein, we have designed a bifunctional Ir₁-In₂O₃ single-atom catalyst, integrating two active catalytic centers by anchoring the monatomic Ir onto the In₂O₃ carrier. This Ir₁-In₂O₃ single-atom catalyst is efficient for the hydrogenation of CO₂ in liquid, yielding a high selectivity for ethanol (>99%) with an excellent initial turnover frequency (481 h^-1). Characterization shows that the isolated Ir atom couples with the adjacent oxygen vacancy forming a Lewis acid-base pair, which activates the CO₂ and forms the intermediate species of carbonyl (CO*) adsorbed on the Ir atom. Coupling this CO* with the methoxide adsorbed on the In₂O₃ forms a C-C bond. The strategy of this effective bifunctional single-atom catalyst by synergistically utilizing the distinct catalytic roles of the single-atom site and the substrates provides a new avenue in catalyst design for complex catalysis.