Cooperative Pyrrolic- and Pyridinic-N Sites in N-Doped Carbons for Efficient CO ₂ Hydrogenation to Formate

Understanding the cooperative roles of nitrogen functionalities in nitrogen-doped carbons (NCs) is crucial for the rational design of efficient catalysts for CO 2 -hydrogenation, yet systematic elucidation of their synergy between pyrrolic-N and pyridinic-N remains limited. Herein, we report a series of RuCl 3 -loaded NCs with precisely tunable N species, fabricated from hyper-cross-linked polymer precursors, and systematically evaluate their performance for CO 2 hydrogenation to formate. Incorporation of benzene-fused units into the polymer framework effectively suppresses N loss during carbonization while inhibiting the conversion of pyrrolic-N to graphitic-N, enabling modulation of the pyrrolic-N fraction up to 78.07% through precursor design and temperature control. Comprehensive experimental analyses combined with density functional theory calculations reveal that pyrrolic-N most effectively promotes CO 2 adsorption and activation, whereas pyridinic-N promotes H 2 dissociation by modifying the electronic state of RuCl 3 . Owing to this synergistic dual-site mechanism, the optimized Ru/PICZ-600 catalyst delivers a high turnover frequency of 1637 h –1 under the selected conditions. This work provides mechanistic insights into N species synergy in carbon-supported catalysis and establishes a general design principle for heteroatom-engineered carbon supports in CO 2 hydrogenation.