Cyclodextrin-assisted defect-rich MoWO_3–x for synergistic adsorption–photocatalytic degradation of organic pollutants

Enhancing the adsorption and photocatalytic degradation of organic pollutants requires simultaneous optimization of interfacial properties and intrinsic electronic structure. Here, we report a one-pot hydrothermal synthesis of γ-cyclodextrin (γ-CD)-assisted molybdenum tungsten oxide (γ-MoWO_3−x), where γ-CD improves surface functionality and induces abundant structural defects. The γ-MoWO_3−x exhibits a 2.9-fold higher surface area and a more negatively charged surface (–27.25 to − 43.02 mV) due to γ-CD–derived hydroxyl groups. Acting as both an in situ reducing agent and defect-inducing molecule, γ-CD generates rich defective oxygen species and partially amorphizes the metal-oxide lattice, effectively tuning the band structure. As a result, γ-MoWO_3−x shows a 3.09-fold enhancement in adsorption–photocatalytic degradation of methylene blue, achieving > 98% removal within 40 min under 1-sun irradiation. Mechanistic studies reveal hole-dominant oxidation pathways. Nanosecond transient absorption spectroscopy Indicates that γ-MoWO_3−x accumulates more photogenerated holes and exhibits a larger proportion of fast hole-decay components, suggesting a higher population of surface-accessible holes that can promote oxidation reactivity. Photoluminescence quenching and electrochemical impedance spectroscopy further indicate suppressed carrier recombination and improved charge mobility. Overall, this work presents a simple and scalable cyclic-oligosaccharide-mediated approach for simultaneous defect and interface engineering, providing valuable design principles for next-generation photocatalysts.