Sulfate radical (SO₄•⁻)-based advanced oxidation processes (SR-AOPs) offer high redox potential, long half-life, and superior selectivity for degrading persistent pollutants in wastewater. However, challenges remain in developing high-activity, recoverable, and reusable catalysts using non-noble metals. Here, we report a high-performance catalyst by immobilizing cobalt pyroborate (Co₂B₂O₅) onto dendritic fibrous silica (KCC-1), enabling efficient peroxymonosulfate (PMS) activation for degrading 4-nitrophenol (4-NP), tetracycline (TC), and sulfamethoxazole (SMX). The optimized Co₂B₂O₅@KCC-1 catalyst (Si/Co = 6, B/Co = 1.5) exhibited 1.6-, 1.9-, and 4.6-fold activity enhancements over CoₓOᵧ@KCC-1, Co₂B₂O₅@MCM-41, and one-pot synthesized Co–B@KCC-1, respectively, underscoring the synergistic benefits of the pyroborate phase and fibrous silica support. This enhanced performance stems from the synergistic integration of redox-active Co₂B₂O₅ with the high-surface-area, radially porous KCC-1 framework, which enables uniform dispersion, increased active site accessibility, and accelerated mass transport. Reactive oxygen species (ROS) trapping and EPR analyses confirmed the generation of surface-bound SO₄•⁻ and singlet oxygen (¹O₂), suggesting coexisting radical and non-radical oxidation pathways. XPS revealed dynamic Co²⁺/Co³⁺ redox transitions during PMS activation, while Bader charge analysis via DFT showed that borate ligands reduce Co electron density by ~0.16 |e| relative to Co₃O₄, facilitating redox cycling. The catalyst exhibited excellent reusability, structural integrity, and retained activity in natural organic matter-rich and river water matrices. This work establishes a foundational platform for high-loading cobalt borates immobilized on fibrous supports, offering a scalable and robust solution for the catalytic degradation of emerging contaminants via sulfate radical-based AOPs.
