Catalyst Design for CO and CO₂ Hydrogenation Reactions: From Microenvironment Engineering to Selectivity Control

The catalytic hydrogenation of CO and CO₂ is fundamental yet practically important in C1 chemistry, leading to sustainable production of fuels and chemicals. A universal challenge across these transformations is precise control over complex reaction networks to achieve high activity and product selectivity. This review focuses on rational catalyst design guided by microenvironment engineering for two representative reactions with complex network, being hydroformylation and CO₂ hydrogenation. We first clarify the distinct chemical nature of CO and CO₂ that dominants divergent catalytic requirements. Then the concept and hierarchical regulation strategies of the catalytic microenvironment is systematically introduced, covering atomic/molecular coordination, nano/micro confinement, and mesoscale interfacial chemistry. For each reaction system, the reaction fundamentals, mechanistic insights, state-of-the-art heterogeneous catalysts, and key structure-performance relationships are summarized. Particular emphasis is placed on how microenvironment modulation, including coordination tuning, spatial confinement, mass transport, and interfacial interactions can determine C-O bond activation, hydrogenation steps, and intermediate stabilization. We further compare catalyst design principles between hydroformylation and CO₂ hydrogenation and highlight the unifying concept of matching C-O activation and hydrogenation capabilities for targeted product distribution. Finally, current limitations and propose future directions is outlined, including in situ characterization, dynamic microenvironment control, single-atom and bimetallic design, zeolite-based confinement, and machine-learning-assisted catalyst development. This review aims to provide a unified mechanistic and strategic framework for advancing selective CO/CO₂ hydrogenation catalysts.