Metal porphyrins and metal phthalocyanines (Pc) constitute a promising class of metal molecular catalysts (MMCs) for efficient CO₂-to-CO electrocatalytic conversion due to their well-defined molecular structures. How to adjust the local coordination and electronic environment of the metal center and enhance the molecular-level dispersion of the active components remains as great challenges for further improving the performance. Herein, a cobalt(II) Pc (CoPc)-COOH/carbon nanotube (CNT)-NH₂ hybrid catalyst was rationally designed by clicking the CoPc-COOH molecules onto the surface of CNT-NH₂ through amidation reaction. This novel hybrid catalyst exhibited the enhanced current density of 22.4 mA/cm² and CO selectivity of 91% at −0.88 V vs. reversible hydrogen electrode (RHE) in the CO₂ electroreduction, as compared with CoPc-COOH/CNT and CoPc/CNT samples. The superior activity was ascribed to the charge transfer induced by introduction of –COOH and –NH₂ functional groups to CoPc and CNT, respectively, facilitating the active centers of Co^I being generated at lower potentials, and leading to the highest turnover frequency (TOF) being obtained over the CoPc-COOH/CNT-NH₂ hybrid catalyst. The inherent directivity and saturability of covalent bonds formed via the amidation reaction ensure not only a higher density of Co active centers, but also an improved stability for CO₂ reduction reaction (CO₂RR). The present study represents an effective strategy for improving MMCs performance by molecular modulating of metal phthalocyanines on functionalized carbon substrates directed by click confinement chemistry.

Over recent years, catalytic materials of Fe-N-C species have been recognized being active for oxygen reduction reaction (ORR). However, the identification of active site remains challenging as it generally involves a pyrolysis process and mixed components being obtained. Herein Fe₃C/C and Fe₂N/C samples were synthesized by temperature programmed reduction of Fe precursors in 15% CH₄/H₂ and pure NH₃, respectively. By acid leaching of Fe₂N/C sample, only single sites of FeN₄ species were presented, providing an ideal model for identification of catalytic functions of the single sites of FeN₄ in ORR. A correlation was conducted between the concentration of Fe^ⅡN₄ in low spin state by Mössbauer spectra and the kinetic current density at 0.8 V in alkaline media, and such a structure-performance correlation assures the catalytic roles of low spin Fe^ⅡN₄ species as highly active sites for the ORR.