Coordination dependent photocatalytic peroxymonosulfate activation on biomass derived Fe single atom catalysts for atrazine degradation

• Biomass derived Fe SACs with varying Fe–N x coordination were synthesized. • Fe–N 6 sites facilitated efficient electron transfer from the CN support to PMS. • Fe–N 6 sites demonstrated high selectivity for 1 O 2 formation. • SA-FeN 6 /CN system achieved over 80 % ATZ degradation in just 15 min. • Three potential degradation pathways, comprising 12 products, were proposed. Challenges associated with uncontrollable metal coordination structures in biomass-derived single-atom catalysts (SACs) and their intricate impacts on photocatalytic peroxymonosulfate (PMS) activation pose significant hurdles for the application of photo-Fenton technology towards wastewater treatment. Herein, we employed a co-pyrolysis strategy using Enteromorpha prolifera ( E. prolifera ) to synthesize Fe SACs with varying Fe–N X coordination, i.e., Fe–N 5 and Fe–N 6 . Fe–N 6 -based SAC achieved over 80 % atrazine (ATZ) degradation in 15 min, with a degradation rate of 0.13 min −1 , representing 2.6-fold improvement over SAC with Fe–N 5 structure. Experimental and simulation results revealed that Fe–N 6 active sites acted as electron donors, enhancing the delocalization of π-electrons and improving photocatalytic PMS activation. This SAC also exhibited high selectivity for 1 O 2 degradation pathway and impressive ATZ degradation in seawater, with notable chlorine resistance, underscoring its potential in environmental pollutant remediation. This work unveils the catalyst structure-photocatalytic PMS activation performance relationship, offering avenue for developing more sustainable and efficient biomass-derived SACs for wastewater treatment.