Harnessing Slow Photons in 3D Silica Photonic Crystals for Efficient and Catalyst-Free Removal of Chromophoric Organic Pollutants

Abstract

The widespread release of chromophoric organic pollutants from industrial and municipal sources poses a critical threat to aquatic ecosystems and human health. While adsorption-based treatments offer rapid contaminant removal, they suffer from limited capacity and secondary waste generation arising from the spent adsorbent. Photocatalytic degradation provides a cleaner alternative but often relies on catalysts with poor stability and slow kinetics. Here in, we introduce a metal-free, catalyst-free water purification approach using chemically inert SiO₂ inverse opal photonic crystals that integrate high-capacity adsorption with visible-light-driven pollutant degradation. The three-dimensional periodic structure facilitates rapid pollutant uptake through interconnected porosity, while photonic bandgap effects and slow photon generation dramatically enhance light confinement. This optical effect enables efficient photodegradation of pre-adsorbed chromophoric organic pollutants using only visible light. Among the tested platforms, SiO₂ IO-343 demonstrates superior performance, achieving >90% adsorption within 1 hour and 95% photodegradation upon extended irradiation. Notably, its apparent reaction rate exceeds those of state-of-the-art semiconductor and hybrid photocatalysts by up to 17-fold, even though it lacks optically active or redox-functional components. Our findings position photonic crystal architectures as a promising class of robust, regenerable, and energy-efficient materials for advanced water treatment, notably offering a catalyst-free alternative for sustainable water purification.