Flexibility-Induced Robustness in Molecular Catalysts for Electrocatalytic CO2 Reduction.

CO2 electroreduction to produce fuels and chemicals is of great significance. Molecular catalysts offer valuable advantages in light of their well-defined active sites and tunable structural and electronic properties. However, their stability is often compromised by rigid conjugated structures. Herein, we proposed a hydrogen-bond regulation strategy that enables reversible structural deformation of metal phthalocyanines (MPcs) by incorporating methoxy groups into the phthalocyanine framework, thereby improving the flexibility and stability of MPcs. Calculations suggested that intermediate absorption induced structural deformation in MPcs. Moreover, hydrogen-bond interactions and conformational changes enriched with substituted methoxy groups in MPcs enhance structural flexibility. Operando Raman studies revealed that these hydrogen bonds correlated with the reversible structural deformation of NiPc. The optimized catalysts, facilitated by hydrogen bonds, achieved stable operation for over 500 h at 100 mA cm-2 with >98% Faradaic efficiency in CO2-to-CO electrocatalytic reduction, significantly outperforming molecular catalysts lacking appropriate hydrogen-bond interactions.