Defect‐Engineered Nested Metallic Cu Clusters Enhance CO ₂ Photoreduction in Photothermal 2D Plasmonic CuSe

ABSTRACT Photocatalytic CO 2 conversion driven by solar energy offers a sustainable pathway for carbon neutrality, but remains limited by inefficient charge dynamics and poor spectral utilization. However, copper chalcogenides exhibit dual UV–vis absorption and near‐infrared (NIR) plasmonic resonance suffer from rapid electron–hole recombination and insufficient catalytic activity. This study introduces nested metallic‐semiconductor Cu‐based heterostructures (Cu/CuSe) synthesized through dissolution–reduction to address these limitations. The engineered architecture incorporates metallic Cu clusters and selenium vacancies within CuSe nanosheets, which collectively broaden NIR absorption through defect‐induced gap states for enhanced photothermal activation. This approach promotes directional electron transfer to Cu clusters, which suppress electron–hole recombination and serve as catalytically active sites. Additionally, seamless coupling between the components lowers interfacial energy losses. Density functional theory calculations reveal that Cu clusters effectively reduce CO 2 activation barriers by stabilizing critical reaction intermediates. The heterostructures achieve a threefold increase in CO yield (27.06 μmol g −1 h −1 ) under full‐spectrum irradiation compared to pristine CuSe, with a 90% selectivity without sacrificial agents. The photothermal–photocatalytic synergy harnesses a cascade energy conversion pathway, outperforming conventional plasmonic semiconductor systems. This work establishes a defect‐engineering strategy to enhance infrared energy harvesting and charge management in broadband‐responsive photocatalysts.