Evaporating water while removing pollutants: nanoconfinement and physical-field regulation enable efficient solar-driven water purification

Can sunlight alone be used to accelerate water evaporation while simultaneously removing organic pollutants? A research team led by Zhongzhen Yu and Jin Qu from Beijing University of Chemical Technology, in collaboration with Zhenzhong Yang’s team at Tsinghua University, has developed a strategy that synergistically combines nanoconfinement with physical-field regulation to integrate efficient solar-driven interfacial evaporation and in situ organic pollutant remediation within a single multifunctional material. Under 1-sun illumination, the three-dimensional evaporator achieved an evaporation rate as high as 6.84 kg m⁻² h⁻¹, while efficiently activating peroxymonosulfate (PMS) for rapid degradation of bisphenol A (BPA), offering a new materials design strategy for solar-driven water purification.

Solar-driven interfacial evaporation converts sunlight into localized thermal energy to promote rapid water vaporization at the air–water interface and has emerged as a promising technology for alleviating freshwater scarcity. However, an efficient solar evaporator must do more than simply absorb light and generate heat. How heat is transferred, how water reaches the evaporation interface, and how rapidly water molecules escape into the vapor phase are equally important in determining overall water production. Moreover, when treating complex water sources such as seawater and industrial wastewater, evaporation alone may be insufficient to address contamination by organic pollutants.

To tackle these challenges, the researchers focused on regulating the nanoscale environment of water molecules. They designed a hollow mesoporous carbon nanocage, termed FCC@Au, in which plasmonic Au nanoparticles are embedded along the inner walls while atomically dispersed Fe–N₄ catalytic sites are incorporated into the carbon framework. This architecture integrates nanoconfinement, photothermal conversion, and catalytic oxidation within a single nanostructure.

The key advantage of the nanocage is that it does not merely “heat” water—it also changes the thermodynamic state of water.

When water enters the mesoporous nanochannels, solid–liquid interfacial interactions and nanoscale curvature reorganize the hydrogen-bond network, converting a larger fraction of bulk water into an intermediate state that can vaporize more readily. This nanoconfinement effect reduces the effective enthalpy of vaporization from a thermodynamic perspective. Meanwhile, under solar irradiation, the embedded Au nanoparticles generate localized surface plasmonic heating, creating local temperature and pressure perturbations across the nanocage that facilitate directional water transport and diffusion.

In other words, nanoconfinement “activates” water, while physical-field perturbations “accelerate” it. Their synergy simultaneously improves the thermodynamics and kinetics of water evaporation.

These nanoscale effects translate into remarkable macroscopic evaporation performance. Under 1-sun illumination, a two-dimensional FCC@Au evaporator achieved an evaporation rate of 2.56 kg m⁻² h⁻¹. When FCC@Au was further integrated with hydrophilic polyurethane foam featuring an open porous network, the three-dimensional configuration expanded the light-receiving and evaporation interfaces, boosting the evaporation rate to 6.84 kg m⁻² h⁻¹.

Importantly, the system is designed not only to evaporate water rapidly but also to remove organic contaminants. Highly accessible Fe–N₄ sites within the nanocages efficiently activate PMS and enable rapid BPA oxidation, predominantly through a non-radical electron-transfer pathway. The mass-normalized rate constant for BPA degradation reached 182.5 L g⁻¹ min⁻¹. In situ Raman spectroscopy, electron paramagnetic resonance measurements, and electrochemical experiments further revealed the surface activation of PMS and the associated electron-transfer process. The system also maintained strong pollutant-removal performance in the presence of different ions, indicating its potential for treating complex water matrices.

In conventional solar water-treatment systems, evaporation and catalytic pollutant degradation are often treated as separate processes. Additional loading or growth of catalysts on porous evaporator substrates can increase fabrication complexity and may introduce trade-offs between different functions. By contrast, FCC@Au integrates photothermal conversion, water-state regulation, accelerated mass transport, and catalytic oxidation within the same nanoscale architecture, allowing solar-driven evaporation and in situ remediation of organic pollutants to proceed simultaneously.

From reorganizing hydrogen-bond networks at the nanoscale and using localized physical fields to accelerate water transport, to employing atomically dispersed Fe–N₄ sites for organic pollutant removal, this work directly connects “evaporation” with “purification.” The study not only provides a new route to overcoming the thermodynamic and kinetic limitations of solar interfacial evaporation, but also highlights the potential of multifunctional photothermal materials for seawater desalination, wastewater treatment, and solar-driven clean-water production, offering new insights into the design of next-generation integrated solar water-purification systems.

Title:Nano-Confined Solar-Thermal Water Purification Boosted by Physical Field Disturbance Coupled with Ultrafast Non-Radical Advanced Oxidation Process

Journal Name: Nano-Micro Letters

DOI: 10.1007/s40820-026-02249-x

URL:https://scholarcast.cast.org.cn/news/2101530345188311040