Highly Transparent Photochromic Coating with Excellent Dimming Capability Based on B─O─W Coordination Bonding Strategy

Photochromic smart windows with efficient solar heat and sunlight modulation are highly sought after for energy efficiency in buildings. However, the preparation of organic-inorganic hybrid photochromic coating with high transparency and excellent dimming ability remains a challenge. Here, we achieve a high dispersion of inorganic nanoparticles in the polymer network based on the B─O─W coordination bond locking strategy, and effectively reduce the energy band gap of Phosphotungstic acid (PTA) by adjusting the local coordination and electronic environment of the metal centre (W) to design a novel conjugated organic-inorganic hybrid photochromic material with high transparency (96.4%), rapid photoresponse (colouring in10 s), and excellent dimming ability (reaching saturation state in 20 min, Visible light modulation range △T_{550 nm} = 87.1%, △T_{749 nm} = 94.0%). Selective heating and cooling of interiors in winter and summer shows excellent potential for improving indoor sunlight comfort and increasing energy efficiency in buildings.