Thermochromic smart windows are widely developed to modulate building energy exchange to save building energy consumption. However, most smart windows have fixed working temperature, moderate energy saving efficiency, and are not suitable for diverse (cold and hot) climates. Here we report smart windows with strong temperature modulation over a broad range by hydrogels with adjustable transition temperatures for all-weather building temperature regulation in different climates. Thermochromic poly(N-isopropylacrylmide-co-N, N-dimethylacrylamide) hydrogels, with lower critical transition temperature ranging from 32.5 to 43.5°C, are developed for smart windows with solar modulation up to 88.84% and intrinsic transmittance up to 91.30% over full spectrum without energy input. Simulated indoor investigations are performed in different cities from 23 °N to 39 °N from winter to summer. The results indicate that the smart windows have a strong solar modulation in summer to reduce indoor temperature up to 7.3°C and efficient heat conservation in winter to save energy up to 4.30 J m?3, in comparison to glass windows. Smart windows with grid patterns and Chinese kirigami are fabricated by using 3D printing of the hydrogels to achieve both solar modulation and light incidence. The strategy offers an innovative path for thermochromic smart windows for low carbon economy.

https://onlinelibrary.wiley.com/doi/10.1002/adma.202211716