The efficient valorization of phenolic compounds derived from coal tar holds strategic importance for advancing national energy development agendas. While substantial progress has been achieved in the separation and purification of these compounds, current research remains largely confined to conventional processing routes, with limited exploration into their integration with sustainable energy systems. Molecular solar thermal (MOST) fuels, a class of organic photo-switchable molecules, undergo reversible conformational transitions upon irradiation at specific wavelengths, storing incident light energy as chemical energy in a high-energy metastable state. Upon appropriate optical triggering, these molecules revert to their ground state with concomitant release of stored energy as heat, completing a closed energy conversion cycle (light → chemical → thermal) that is inherently free of greenhouse gas emissions. phenolic compounds recovered from coal tar or phenolic oil fractions were employed as feedstocks to synthesize a series of environmentally benign azo-based MOST fuels via diazo coupling reactions. Owing to the exceptional photo-reversible conformational isomerization characteristics of the azo chromophores, the synthesized materials achieved an energy storage density as high as 162 kJ mol⁻¹ under ultraviolet irradiation, with the stored energy exhibiting stability over several months. Upon excitation with blue light, the photothermally released energy raised the material temperature by 9–16 °C, underscoring their considerable potential in intelligent thermal regulation applications. Notably, the resulting azo-based fuels demonstrated an approximate 20-fold increase in product value relative to the parent phenolic compounds. The strategy proposed herein not only elevates the economic worth and functional applicability of key coal tar constituents but also furnishes a theoretical foundation and technical framework for process innovation and high-value development within the coal tar industry.

Coal tar; phenolic compounds; solar thermal fuels; molecular energy storage; photoisomerization