During the catalytic process, the microenvironment and surface area of the catalyst will affect the catalytic performance. Hence, an assisted organic linker coated metal-organic framework (MOF) has been applied, to form Ni/HNC (HNC represents hollow nanocage) for electrocatalytic CO₂ reduction. Remarkably, Ni/HNC achieves superb activity with high Faradaic efficiency (FE) of 97.2% at 0.7 V vs. reversible hydrogen electrode (RHE) towards CO₂ conversion to CO. In contrast to Ni/NPC (afforded from the naked MOF), the Ni/HNC displays higher FE and selectivity on CO rather than H₂, owing to the large nanocage which extraordinarily facilitates CO₂ enrichment and the active sites easily accessible. This work provides a general and feasible route to construct high-efficient electrochemical CO₂ reduction reaction (EC-CO₂RR) catalysts via post-modified MOFs.

Fine regulation of geometric structures has great promise to acquire specific electronic structures and improve the catalytic performance of single-atom catalysts, yet it remains a challenge. Herein, a novel seed encapsulation–decomposition strategy is proposed for the geometric distortion engineering and thermal atomization of a series of Cu-N_x/S moieties anchored on carbon supports. During pyrolysis, seeds (Cu²⁺, CuO, or Cu₇S₄ nanoparticles) confined in metal organic framework can accommodate single Cu atoms with Cu–N or Cu–S coordination bonds and simultaneously induce C–S or C–N bond cleavage in the second coordination shell of Cu centers, which are identified to manipulate the distortion degree of Cu-N_x/S moieties. The severely distorted Cu-N₃S molecular structure endows the resultant catalyst with excellent oxygen reduction reaction activity (E_1/2 = 0.885 V) and zinc-air battery performance (peak power density of 210 mW·cm⁻²), outperforming the asymmetrical and symmetrical Cu-N₄ structures. A combined experimental and theoretical study reveals that the geometric distortion of Cu-N_x/S moieties creates uneven charge distribution by a unique topological correlation effect, which increases the metal charge and shifts the d-band center toward the Fermi level, thereby optimizing the inter-mediate adsorption energy.