Ultra-wide temperature cycle control based on photo-responsive phase change†

The working principles of temperature control systems differ strikingly under severe temperature conditions. Thus, effective cooling is the main requirement for temperature control at high temperatures, whereas heating is the main concern at low temperatures. Consequently, the simultaneous combination of the heating and cooling functions in the same material at high and low temperatures is a challenging task. In this study, a series of composite aerogels comprising boron nitride–polyvinyl alcohol (BN–PVA) aerogels and Azo-OCn (n = 6, 8, 10 and 12) photo-responsive phase-change materials with energy cycle control capabilities from low to high temperatures (−20 °C to 80 °C) were prepared. The resulting BN–PVA/Azo-OCn composite aerogels achieve high enthalpy energy storage (up to 284.7 J g⁻¹) and tunable photo-responsive response time (half-life from 6.88 min to 175.04 h). Compared with the BN–PVA aerogel, the BN–PVA/Azo-OCn composite aerogels achieve temperature control with low-temperature heat release (an increase of 22.45 °C) and high-temperature heat absorption (a decrease of 11.88 °C) over an ultra-wide temperature range from −20 °C to 80 °C. An unprecedented ultra-wide range of temperature control has been achieved. This study provides new strategies for the future development of intelligent, highly thermally conductive and thermally controllable materials within an ultra-wide temperature range.