Electro/photocatalytic carbon dioxide (CO₂) reduction to value-added chemicals and fuels is being actively studied as a promising pathway for renewable energy storage and climate change mitigation. Because of inert molecular properties and competing hydrogen generation reactions, high-performance electrocatalysts with high Faradaic efficiency and product selectivity but low overpotential are urgently needed. Polyoxometalates (POMs) are a class of polynuclear metal oxide clusters with a precise atomic structure, providing an ideal research platform to reveal the relationship between macroscopic properties and microstructures. Moreover, their highly tunable redox properties and abundant transition metal atom composition ensure thriving research for POM-based nanostructures toward CO₂ reduction. In this review, we first introduce the specific roles of POMs in electro/photocatalytic CO₂ reduction. Recent advances in POM-based nanostructures ranging from single clusters, assemblies, organic–inorganic hybrids to derivatives are systematically summarized. In particular, the structure–performance relationship of POM-based nanostructures is discussed at the atomic and molecular levels. Finally, the challenges and opportunities in the design of high-efficiency POM-based nanostructures are discussed to promote electro/photocatalytic CO₂ reduction.

Electroreduction of greenhouse gas CO₂ into value-added fuels and chemicals provides a promising pathway to address the issues of energy crisis and environmental change. However, the regulations of the selectivity towards C₂ product and the competing hydrogen evolution reaction (HER) are major challenges for CO₂ reduction reaction (CO₂RR). Here, we develop an interface-enhanced strategy by depositing a thin layer of nitrogen-doped graphene (N-G) on a Cu foam surface (Cu-N-G) to selectively promote the ethanol pathway in CO₂RR. Compared to the undetectable ethanol selectivity of pure Cu and Cu@graphene (Cu-G), Cu-N-G has boosted the ethanol selectivity to 33.1% in total Faradic efficiency (FE) at −0.8 V vs. reversible hydrogen electrode (RHE). The experimental and density functional theory (DFT) results verify that the interconnected graphene coating can not only serve as the fast charge transport channel but also provide confined nanospace for mass transfer. The N doping can not only trigger the intrinsic interaction between N in N-G and CO₂ molecule for enriching the local concentration of reactants but also promote the average valence state of Cu for C–C coupling pathways. The confinement effect at the interface of Cu-N-G can not only provide high adsorbed hydrogen (H_ad) coverage but also stabilize the key *HCCHOH intermediate towards ethanol pathway. The provided interface-enhanced strategy herein is expected to inspire the design of Cu-based CO₂RR electrocatalysts towards multi-carbon products.