Abstract As a very promising thermochromic material, VO2 (M/R) (Monoclinic/Rutile) has not been widely applied in smart windows due to its intrinsic low solar modulation (ΔTsol) and low luminous transmission (Tlum). To address this issue, porous structures have been introduced into the VO2 film. Herein, mesoporous VO2 powders with pore size of about 2–10 nm were synthesized using cotton as template by hydrothermal methods. The pore and crystal size of the synthesized VO2 powders can be reliably controlled by the hydrothermal temperature. The mesoporous VO2 powders were mixed with PVP to prepare the VO2-based nanocomposite films by spin coating. The VO2-based films show a better performance between ΔTsol and Tlum than that appeared in previous reports. Especially, a larger pore size could lead to a higher visible transmittance and a larger crystal size would facilitate the enhancement in the solar modulation. In this sense, the VO2-based film obtained at the hydrothermal temperature of 180 °C exhibits an outstanding thermochromic performance with ΔTsol of 12.9% and Tlum up to 56.0% due to a larger crystal size and pore size. Therefore, this synthetic route shows a potential method for the application of mesoporous VO2 powders for solar control coatings.

中文翻译：

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棉模板法合成介孔VO 2 纳米晶体及其增强的热致变色性能

摘要 VO2 (M/R) (Monoclinic/Rutile) 作为一种非常有前景的热致变色材料，由于其固有的低太阳调制 (ΔTsol) 和低透光率 (Tlum) 尚未广泛应用于智能窗户。为了解决这个问题，已经在 VO2 薄膜中引入了多孔结构。在此，以棉花为模板，通过水热法合成了孔径约为 2-10 nm 的介孔 VO2 粉末。合成的 VO2 粉末的孔隙和晶体尺寸可以通过水热温度可靠地控制。将介孔 VO2 粉末与 PVP 混合，通过旋涂制备 VO2 基纳米复合薄膜。基于 VO2 的薄膜在 ΔTsol 和 Tlum 之间显示出比之前报告中出现的更好的性能。尤其，较大的孔径会导致更高的可见光透射率，较大的晶体尺寸会促进太阳能调制的增强。从这个意义上说，在 180 °C 的水热温度下获得的 VO2 基薄膜表现出出色的热致变色性能，由于更大的晶体尺寸和孔径，ΔTsol 为 12.9%，Tlum 高达 56.0%。因此，该合成路线显示了将介孔 VO2 粉末应用于阳光控制涂料的潜在方法。