Materials Innovation and the Changing Face of Photocatalytic and Electrocatalytic Carbon Dioxide Reduction Research: From Metal Nanoclusters to Extended Frameworks

The accelerating rise in atmospheric CO₂ levels, driven by anthropogenic emissions, underscores the urgent need for transformative carbon management strategies. Photocatalytic and electrocatalytic CO₂ reduction reactions (CO₂RRs) offer a promising route to valorize CO₂ into energy-rich fuels and chemical feedstocks, yet the intrinsic thermodynamic and kinetic barriers necessitate catalysts that combine high activity, selectivity, and durability. Recent breakthroughs in materials chemistry have spotlighted two emerging material classes-atomically precise metal nanoclusters (NCs) and extended reticular frameworks such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs)-as frontiers for next-generation CO₂RR catalysts. Both systems offer unparalleled opportunities to engineer active sites at the atomic and molecular levels, enabling precise modulation of local environments, electronic structures, and substrate interactions. This review brings these two materials paradigms under a common vision of precision-controlled catalysis, highlighting how innovations in cluster size, framework topology, and chemical functionality dictate product selectivity and C─C coupling behavior. We discuss emerging mechanistic insights, synthetic strategies, and structure-function relationships and outline challenges in conductivity, stability, and scalability. Finally, we propose integrated design principles to guide the development of hybrid platforms for efficient and selective CO₂ valorization.