Biomimetic spatial compartmentalization directs C1 intermediate evolution for highly selective CO2 photomethanation.

Photoreduction of CO2 and H2O to CH4 offers a sustainable pathway for solar-to-chemical energy conversion. However, premature desorption of the CO* intermediate before coupling with protons (H*) to form a CHO* intermediate remains a major bottleneck, severely suppressing CH4 selectivity. Herein, we design a novel biomimetic "nucleus-cytoplasm" configuration photocatalyst, Pd1(C)/Ns/CNNs, where atomically dispersed Pd single atoms (Pd1(C)) serve as the cytoplasm for selective CO2 activation, while the adjacent Pd nanosheets (PdNs) act as the "nucleus" to supply H* and catalyze downstream hydrogenation. This configuration induces a short-range internal electric field, analogous to intracellular signaling, which synchronizes electron-H* transfer, facilitates directional CO* migration toward the "nucleus", and restrains premature desorption, enabling CHO* formation seamlessly. Experimental results and density functional theory calculations show that Pd1(C) binds and activates CO2, while PdNs stabilize CO* and promote H2O dissociation to generate H*. Ab initio molecular dynamics simulations capture the CO*-H* coupling into CHO*, directly visualizing this key transformation step. As a result, the Pd1(C)/Ns/CNNs achieves an outstanding CH4 evolution rate of 876.8 µmol g-1 h-1 with nearly 100% selectivity. This work introduces a biologically inspired spatial design that regulates intermediate evolution via local electronic synergy, providing a new idea for highly efficient and selective CO2 photomethanation.