Metal-Free PMS Activation by Heterocycle Porous Aromatic Frameworks for Contaminant Degradation.

Heteroatoms in heterocycles significantly modify the redox properties of the catalysts, thus exhibiting high efficiency, environmental friendliness, and applicability in advanced oxidation processes (AOPs) without metals. Therefore, a porous aromatic framework (PAF-146) rich in N and S atoms was synthesized from heterocycle building units and exhibited excellent stability. Benefiting from the stability and catalytic activity of PAF-146, it demonstrated a catalytic performance of degrading 99.7% of Rhodamine B (RhB) within 20 minutes, with a reaction rate constant 95 times higher than that of pristine PAF without N and S atoms. Moreover, PAF-146 exhibited good resistance to interference from anions, different aquatic environments, and humic acid (HA). The strongly electronegative N and S atoms in PAF-146 initiated the redistribution of charge density, resulting in positively charged adjacent C atoms. Peroxymonosulfate (PMS) underwent a nucleophilic addition reaction on these C atoms, triggering electron transfer and ultimately leading to the formation of ¹O₂ and O₂ ^•-. It was revealed that PAF-146 achieved efficient degradation of RhB through a combination of radical and nonradical pathways. Our work provides guidance for the development of efficient metal-free catalysts with abundant catalytic sites for PMS-activation in environmental remediation.