Molecularly Engineered Co-Phthalocyanine Covalent Organic Frameworks for Efficient Nitric Oxide-to-Ammonia Electroreduction

Electrocatalytic nitric oxide reduction reaction (NORR) represents a promising strategy for sustainable ammonia synthesis coupled with the removal of the NO pollutant in flue gas. However, current electrocatalysts still suffer from a lack of accuracy in regulating the binding strength between catalytic sites and NORR intermediates, which is crucial for optimizing the ammonia yield and Faradic efficiency (FE). Herein, we constructed Co-phthalocyanine covalent organic frameworks with integrated boron and fluorine (BF-COF) via a molecular engineering strategy to modulate the reaction microenvironment, thus effectively and precisely tuning the interactions between NO molecules and the catalytic interface. The BF-COF is shown to be beneficial for the formation of *HNO and the desorption of *NH₃ intermediate, thus exhibiting an ammonia yield of 1166.67 μg cm^-2 h^-1 and FE of 82.27%, surpassing its counterparts B-COF and F-COF. Our results constitute the first experimental example of COFs for NORR while outperforming most reported electrocatalysts for this reaction. In situ characterizations and theoretical calculations elucidate that Co sites facilitate adsorption and activation of NO, while pyrrole-N sites synergistically mediate water adsorption and dissociation, establishing a proton-rich microenvironment and accelerating interfacial proton transfer. Our findings provide molecular-level insights into the precise modulation of interactions between NO and catalytic interfaces, accelerating interfacial mass transfer kinetics in the NORR process.