Nanoscale greenhouse effect for promoting solar-driven CO2 reduction with water to CH4

Improvement of solar-to-chemical energy conversion in photocatalytic CO₂ reduction remains fundamentally constrained by insufficient utilization of solar energy, particularly low-energy photons. Here we report a nanoscale greenhouse structure (Bi@Fe₂O₃) that enables cascaded utilization of full solar spectrum. The Bi nanocore primarily absorbs low-energy photons, generating localized nanoheating via non-radiative heating through localized surface plasmon resonance effects and energetic hot electrons. Meanwhile, the oxygen-vacancy-rich loose Fe₂O₃ shell absorbs high-energy photons and serves as the catalytic bed, where injected hot electrons and confined heat synergistically promote CO₂ activation and deep hydrogenation. Benefiting from the interplay between photochemical and photothermal effects, the system achieves a CH₄ production rate of 273.81 μmol g^-1 h^-1 with 98.60% selectivity and an apparent quantum efficiency of 0.64% at 850 nm illumination without any external heating or sacrificial agents. This work paves a way for the efficient utilization of the entire solar spectrum.