Key Takeaways & Executive Findings
- •• • The UiO-66@dye-2 system achieves a solar-to-vapor conversion efficiency of 97.8% under 1-sun irradiation, significantly outperforming conventional photothermal materials and enabling high-yield freshwater production in energy-scarce regions. • • Photocatalytic degradation of phenol reaches 95.4% under the same conditions, demonstrating dual functionality that addresses both water scarcity and organic pollutant removal in a single solar-driven process. • • The material maintains stable degradation performance across highly acidic and alkaline environments, indicating robust chemical durability essential for treating industrial effluents with extreme pH values. • • Defect engineering via covalent dye anchoring introduces abundant trap sites, facilitating rapid charge transfer and efficient spatial charge separation, which is critical for achieving high quantum efficiency in photocatalytic reactions.
Abstract
Solar interfacial evaporation and photocatalysis exhibit intrinsic complementarity in energy utilization pathways and reaction mechanisms. Integrating photocatalysis into interfacial evaporation systems enables a synergistic platform for efficient evaporation and pollutant removal. In this study, a defect-engineering strategy is developed for UiO-66 by covalently anchoring five carboxyl-containing organic dyes into its framework, where steric hindrance and ligand substitution synergistically induce abundant structural defects. This approach yields a series of defect-rich UiO-66 materials with tunable dye loading. Among them, the dye-sensitized UiO-66@dye-2 system demonstrates optimal light absorption capacity and vacancy defects. The dyes act as sensitizers, broadening the light absorption range and accelerating water evaporation, while the defect-inducing dyes introduce abundant trap sites, enabling rapid charge transfer and efficient spatial charge separation. Under 1-sun irradiation, the system achieves an outstanding water evaporation rate with a high solar-to-vapor conversion efficiency of 97.8%, along with excellent photocatalytic performance, achieving 95.4% degradation of phenol pollutants. Notably, it maintains stable degradation performance across highly acidic and alkaline environments, ensuring reliability for long-term operations in complex conditions. This work provides a molecular-level strategy for constructing defect-rich UiO-66 derivatives and offers insights for designing next-generation materials for integrated photothermal-photocatalytic environmental remediation.
1. Introduction
Conventional photothermal evaporators primarily harness visible and near-infrared light, leaving ultraviolet photons untapped and failing to degrade volatile organic compounds (VOCs) that often accompany contaminated water sources. This limitation restricts overall water purification efficiency and necessitates additional treatment steps. Physically assembled heterostructures, while attempting to couple photothermal and photocatalytic functions, suffer from weak interfacial coupling, leading to inefficient solar energy utilization, structural instability, and potential secondary pollution. These drawbacks have hindered the deployment of integrated solar-driven water purification systems in real-world scenarios.
The present work addresses this bottleneck by employing in-situ defect engineering within a metal-organic framework (UiO-66). By covalently anchoring carboxyl-containing organic dyes, the framework is endowed with abundant structural defects that simultaneously broaden light absorption and introduce trap sites for charge separation. This molecular-level strategy ensures strong interfacial coupling and chemical robustness, enabling the material to achieve both high evaporation efficiency and photocatalytic degradation of phenol pollutants under 1-sun irradiation. The approach offers a scalable pathway to design next-generation materials for integrated photothermal-photocatalytic environmental remediation.
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Tiantian Wu, Yatong Wang, Yaning Xu, Tianhao Shen, Ranwei Zhang, Shiyan Ai, Qing Huang, Qi Zhang, Lixing Kang, Dan Tian (2026). Adjusting Light Absorption of Defective UiO-66 for Coupling Photothermal Evaporation with Photocatalysis. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4209-3
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Frequently Asked Questions
What is the long-term stability of the UiO-66@dye-2 system under continuous solar irradiation and in corrosive environments?
The material maintains stable photocatalytic degradation performance across highly acidic and alkaline environments, indicating robust chemical durability. However, the abstract does not specify the duration of long-term operations; further testing under continuous 1-sun irradiation and cyclic use is necessary to confirm mechanical and photostability.
How does the dye loading affect the defect density and the resulting photothermal and photocatalytic performance?
The study systematically regulates the dye content to produce a series of defect-rich UiO-66 materials. The optimal system, UiO-66@dye-2, exhibits the best light absorption and vacancy defects, leading to a solar-to-vapor efficiency of 97.8% and 95.4% phenol degradation. This suggests an optimal balance between dye sensitization and defect introduction; excessive dye may block active sites or reduce structural integrity.
What is the scalability potential of this defect-engineering approach for industrial-scale water purification?
The synthesis involves covalent anchoring of organic dyes into UiO-66, which is a scalable process using solvothermal methods. However, the cost of dyes and MOF precursors, as well as the need for large-area evaporator fabrication, must be considered. The high efficiency under 1-sun irradiation suggests potential for passive solar devices, but pilot-scale testing is required to assess economic viability.
How does the photocatalytic degradation of phenol compare to other advanced oxidation processes in terms of kinetics and mineralization?
The abstract reports 95.4% degradation of phenol, but does not specify the degradation rate constant or the extent of mineralization (e.g., TOC removal). For practical applications, complete mineralization to CO2 and H2O is preferred to avoid toxic intermediates. Further studies should measure total organic carbon (TOC) and identify intermediate products.
What is the mechanism of charge transfer and separation in the defective UiO-66@dye-2 system?
The defect-inducing dyes introduce abundant trap sites that facilitate rapid charge transfer and efficient spatial charge separation. The dyes act as sensitizers, broadening light absorption and injecting electrons into the UiO-66 framework. The defects likely act as electron traps, reducing recombination and enhancing photocatalytic activity. Detailed spectroscopic studies (e.g., transient absorption, photoluminescence) would provide deeper insight.
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