Near Infrared-Blocking Thermochromic Hydrogel Smart Windows for Passive Solar Heat Control

Abstract Excessive solar heat gain through transparent enclosures is a critical challenge for buildings, vehicles, and greenhouse agriculture, particularly in hot-arid regions where indoor overheating increases the demand for energy- and water-intensive cooling. Herein, we report an interpenetrating-network thermoresponsive hydrogel smart window that passively regulates greenhouse heat gain through thermochromic solar modulation and nanomaterial-enabled near-infrared attenuation. The incorporation of Cs0.33WO3 nanoparticles into the hydrogel endows it with strong near-infrared (NIR) absorption, blocking 89.6% of incident NIR radiation and promoting rapid thermochromic switching under solar illumination. As a result, the hydrogel window delivers high solar transmittance modulation capability (37.5%) while maintaining large luminous transmittance (74.3%), allowing sufficient transmission of visible light for plant photosynthesis. Additionally, a gel−air bilayer architecture is designed to enhance thermal insulation under hot-arid conditions. Greenhouse cultivation in Saudi Arabia is employed as a practical testbed to evaluate the effectiveness of the proposed solar management strategy. The proposed hydrogel smart window reduces soil temperature in a greenhouse by up to 12 °C and improves crop yield by 66.7% compared with conventional plastic panels. Overall, this work establishes a passive, climate-adaptive smart-window strategy for thermal management in greenhouses and sustainable crop production in extreme environments.