Rotating Pyridone-Induced 4-Fold Interpenetrated CoII-Porphyrin Hydrogen-Bonded Organic Framework for Efficient CO₂ Electroreduction

Examples of hydrogen(H)-bonded organic frameworks (HOFs) employed in the field of catalysis are rare, especially in terms of the potential for using hydrogen bonding in electrocatalytic processes. For mimicking the linking modes of multi-H-bonds in DNA base pairs owning specific CO2 adsorption capacity to construct HOFs with a more stable stacking structure, herein, CoII-5,10,15,20-tetra(4-hydryl-3-pyridyl)porphyrin (CoTOPyP) is designed and synthesized and then successfully crystallized into the HOF (HOF-CoTOPyP), where CoII-porphyrin units are interconnected via rotating pyridone-induced H-bonds, creating a tetra-coordinated, interpenetrated framework. The resulting HOF-CoTOPyP exhibits excellent electrocatalytic reduction of carbon dioxide (CO2ER) performance with a CO Faradaic efficiency [FE(CO)] of up to 98%. Mechanistic and theoretical studies reveal a transformative innovation: the HOF's unique architecture with rotational pyridones can facilitate CO2 adsorption and transport, as well as product evolution during the CO2ER process, where there exist two distinct CO intermediates, atop-adsorbed CO (COatop) and H-bond linked CO (COH-Bonding), and the latter plays a dominant role via a H-bond promotion CO2ER mechanism. The present study not only deepens our mechanistic understanding of how to enhance the CO2ER performance via H-bonding but also provides valuable insights for the future design and development of advanced HOFs with structural and functional versatilities for broader catalytic applications.