Hydrogel-based building envelope with dual regulation of light quantity and quality for healthy lighting and energy saving

The building envelope based on thermochromic hydrogels provide a promising strategy for the dynamic regulation of solar radiation. However, traditional thermochromic hydrogels can only regulate the intensity of visible light and cannot regulate the spectrum to meet the requirements of human life and plant growth. Here, we report a scalable and potentially cost-effective light-conversion thermochromic hydrogel (LCTH) that combines thermo-responsive reversible volume phase transition with the photoluminescent down-conversion effect, achieving adaptive regulation of solar intensity and selective spectral conversion. Under thermal stimulation, the LCTH exhibits a solar regulation capacity of 54.8% and a visible light regulation capacity of 73.3%. Furthermore, under ultraviolet irradiation, it absorbs 89.2% of ultraviolet and harmful blue light, and achieves a quantum yield of 43.01%. Experimental results showed that, compared with commercial glass, the LCTH effectively protects plants from UV damage. At noon, it achieves an average cooling effect of 4.43 °C and a maximum cooling of 10.7 °C, thus alleviating heat stress in plants. In addition, the energy consumption analysis was carried out by establishing a sunroom model. The results showed that in Riyadh, the large-scale application of LCTHs as building envelope is expected to reduce CO₂ emissions by 17845 kg annually for a 100 m² sunroom building. This study presents an alternative scheme for building transparent envelopes with dual control capabilities over light quantity and quality, providing a novel strategy for healthy lighting and low-carbon energy saving in buildings.