Hydrogen‐Bond‐Assisted Perylene Diimide/Alginate Supramolecular Aerogels for Coupled Radical–Nonradical Peroxydisulfate Activation

Abstract

Photocatalytic peroxydisulfate (PDS) activation can proceed via radical and nonradical pathways, yet integrating these processes in transition‐metal‐free photocatalysts remains challenging. Here, a perylene diimide/sodium alginate supramolecular aerogel (PDI2/ALG) was prepared by acid‐induced co‐assembly and freeze‐drying. Structural characterization shows that ALG incorporation reorganizes PDI molecular packing while retaining local π‐stacked order and produces a hierarchical PDI/ALG interface. The available donor and acceptor groups are consistent with proposed interfacial hydrogen‐bonding motifs. Relative to pristine PDI, PDI2/ALG exhibits a 44% higher photocurrent, a modestly lower charge‐transfer resistance, an optical band gap of 1.66 eV, and an absorption edge extending to approximately 750 nm. Under visible‐light irradiation, addition of PDS increases tetracycline (TC) degradation to 90.6% within 30 min, and the catalyst retains more than 85% of its initial activity after five cycles. Scavenger, electron paramagnetic resonance (EPR) spin‐trapping, fluorescence‐probe, and electrochemical measurements support concurrent oxygen activation, PDS reduction, and hole‐mediated oxidation, with O2•−, 1O2, SO4•−, and •OH participating in coupled radical and nonradical pathways. Degradation performance varies markedly across different pollutants, while density functional theory (DFT) –derived descriptors and liquid chromatography‑mass spectrometry (LC‐MS) analysis indicate pollutant‐dependent electronic susceptibility and multiple plausible TC transformation pathways. These results show that PDI/ALG supramolecular co‐assembly can tune molecular packing and interfacial properties to support coupled radical–nonradical PDS activation.