Turning NOx Pollutants into Green Ammonia Fuel via COF Cavity Confinement

The development of sustainable fuels and hydrogen carriers is essential for a carbon-neutral energy future. Ammonia (NH3) is a promising energy vector, yet its synthesis remains dependent on the energy-intensive Haber–Bosch process, while nitrogen oxides (NOx) persist as major atmospheric pollutants. In this work, spin-polarized density functional theory (DFT) calculations at the MPWB1K/def2SVP level are used to investigate the capture and reduction of NO and NO2 within a rigid covalent organic framework (M1). Nucleus-Independent Chemical Shift (NICS) analysis reveals a strongly aromatic shielding character (NICS = −10.8) that provides a unique electronic environment, while electrostatic potential (ESP) mapping illustrates local electron density. Confinement within the framework suppresses competing pathways that preferentially favor the pathway toward NH3 and H2O. Activation barriers are significantly reduced, driven by charge transfer that weakens N–O bonds. The rigid covalent organic framework remains structurally stable throughout the process. These findings demonstrate a viable strategy for converting atmospheric pollutants into valuable energy carriers under moderate thermal activation.