3D mesoporous structure assembled from monoclinic M-phase VO₂ nanoflakes with enhanced thermochromic performance

Monoclinic M-phase VO₂ is a promising candidate for thermochromic materials due to its abrupt change in the near infrared (NIR) transmittance along with the metal-to-insulator transition (MIT) at a critical temperature ∼68 °C. However, low luminous transmittance (T _lum), poor solar energy modulation ability (ΔT _sol), and high phase transition temperature (T _c) can limit the application of VO₂ for smart windows. To overcome these limitations, 3D mesoporous structure can be employed in VO₂ films. Herein, 3D mesoporous structures assembled from monoclinic M-phase VO₂ nanoflakes with a pore size of about 2-10 nm were synthesized by a hydrothermal method using Ensete ventricosum fiber (EF) as a template followed by calcination at 450 °C. The prepared film exhibited excellent thermochromic performance with balanced T _lum = 67.3%, ΔT _sol = 12.5%, and lowering T _c to 63.15 °C. This is because the 3D mesoporous structure can offer the uniform dispersion of VO₂ nanoflakes in the film to enhance T _lum, ensure sufficient VO₂ nanoflakes in the film for high ΔT _sol and lower T _c. Therefore, this work can provide a green approach to synthesize 3D mesoporous structures assembled from monoclinic M-phase VO₂ nanoflakes and promote their application in smart windows.