Donor-acceptor conjugated organic polymers for light-driven durable and direct air-to-nitric acid conversion

The production of nitric acid directly from ambient air offers a promising pathway for ammonia-free synthesis of this essential chemical. Herein, we report a donor-acceptor conjugated porous organic polymer that enables durable and direct photosynthesis of nitric acid from air at room temperature. Remarkably, the polymer maintains high catalytic activity even after 324 h of light irradiation, achieving a substantial nitric acid yield up to 4466.2 μmol·g⁻ 1 cat . The reaction mechanism underlying the photocatalytic nitric acid synthesis is systematically investigated through a combination of experimental studies and theoretical calculations. Additionally, the reaction intermediates are monitored by NMR, EPR, MS and DRIFTS. Based on the results, a reaction pathway involving O 2 reduction, in situ •OH generation and N 2 oxidation at the acceptor site of the polymer is proposed. This work presents a metal-free photocatalytic process for the direct synthesis of nitric acid from air under mild conditions.