Single-Atom Metal Anchored Zr 6 -Cluster-Porphyrin Framework Hollow Nanocapsules with Ultrahigh Active-Center Density for Electrocatalytic CO 2 Reduction.

Designing earth-abundant electrocatalysts toward highly efficient CO 2 reduction has significant importance to decrease the global emission of greenhouse gas. Herein, we propose an efficient strategy to anchor non-noble metal single atoms on Zr 6 -cluster-porphyrin framework hollow nanocapsules with well-defined and abundant metal-N 4 porphyrin sites for efficient electrochemical CO 2 reduction. Among different transition metal single atoms (Mn, Fe, Co, Ni, and Cu), Co single-atom anchored Zr 6 -cluster-porphyrin framework hollow nanocapsules demonstrated the highest activity and selectivity for CO production. The rich Co-N 4 active centers and hierarchical porous structure contribute to enhanced CO 2 adsorption capability and moderate binding strength of reaction intermediates, thus facilitating *CO desorption and CO 2 -to-CO conversion. The Co-anchored nanocapsules maintain high efficiency and well-preserved stability during long-term electrocatalysis tests. Moreover, the Co-anchored nanocapsules exhibit a remarkable solar-to-CO energy conversion efficiency of 12.5% in an integrated solar-driven CO 2 reduction/O 2 evolution electrolysis system when powered by a custom large-area [Cs 0.05 (FA 0.85 MA 0.15 ) 0.95 ]Pb 0.9 (I 0.85 Br 0.15 ) 3 -based perovskite solar cell.