Metamaterial-Enhanced Solar-Driven Processes for Energy Conversion and Water Treatment.

To address global challenges in sustainable energy and water treatment, metamaterials have emerged as a transformative class of materials for solar-driven photocatalysis. Through nanoscale engineering, these artificially structured materials enable precise manipulation of light-matter interactions and significantly enhance solar energy utilization beyond the limits of conventional photocatalysts. This review systematically summarizes recent progress in applying metamaterials to solar-driven processes for energy conversion and water treatment, including photocatalytic CO reduction, water splitting for hydrogen generation, degradation of organic pollutants, and solar-driven water evaporation for purification. Key enhancement mechanisms include localized surface plasmon resonance, photonic bandgap engineering, and improved charge separation via metamaterial and semiconductor heterojunctions, which collectively improve light absorption, charge separation and transfer, and surface reactivity. Practical challenges related to scalable fabrication, long-term durability, and integration into real-world systems are also examined. Finally, emerging directions, including AI-assisted inverse design, structural chirality, and multifunctional hybrid architectures, are discussed as promising strategies to further advance metamaterial-based photocatalysts in sustainable energy and environmental applications.