From Sunlight to Heat on Demand: Azo-Switches for Efficient and Robust Molecular Solar Thermal Fiber

Molecular solar thermal (MOST) materials, capable of harvesting solar energy and releasing it as heat on demand, hold great potential for personal thermal management (PTM), especially in wearable fabrics. However, creating MOST fabrics that can efficiently capture natural sunlight, achieve high energy-storage capacity, and maintain long-term stability remains challenging due to the narrow absorption range, low energy density, and leakage risks of current materials. This project aims to establish a zero-emission, wearable MOST energy storage platform for PTM. Its overarching goal is to design, synthesize, and demonstrate a new generation of robust azobenzene-based photoswitches and fiber-integrated devices capable of capturing natural sunlight, storing thermal energy for extended periods, and releasing it controllably on demand. To achieve this, WP1 focuses on the molecular design and synthesis of sunlight-responsive photoswitches with enhanced visible-light absorption and improved thermal stability. WP2 develops phase-change energy storage strategies through hydrogen-bond engineering and molecular packing optimization to maximize energy density, with encapsulation ensuring durability and leak prevention. WP3 integrates optimized materials into coaxial fibers with near-infrared absorbers for broad-spectrum solar harvesting and scalable device fabrication. Supporting activities include WP4 on training and skills development, WP5 on knowledge dissemination and exploitation, and WP6 on public engagement. MOSTF will push the boundaries of current technology by broadening solar spectral coverage, achieving >0.4 MJ/kg energy storage densities, and delivering wearable fiber-based devices capable of 1,000+ stable charge–release cycles. The project directly supports the Horizon Europe Work Programme on sustainable energy, advanced materials, and innovation, contributing to UN SDG 7 (Affordable and Clean Energy) and SDG 9 (Industry, Innovation and Infrastructure).