Sustainable Conversion of Elemental Sulfur to Fluorescent Luminophore

Abstract The strong reliance on oil and gas necessitates continuous refinery operations, resulting in the unregulated and sustained production of byproducts such as elemental sulfur (S8), thereby posing significant management challenges. Converting this byproduct into valuable materials through sustainable, environmentally friendly methods offers a promising solution by reducing costs, health risks, and processing challenges. As the field of light-emitting materials continues to expand globally, the demand for sustainable, stable, and efficient optoelectronic materials is steadily increasing. Herein, we report the mechanochemical synthesis of luminescent N-heterocyclic chalcogenones, hexaphenylpyridineimidazolthione (HPPIT) and hexaphenylpyridineimidazolselone (HPPIS). The material is readily synthesized by mechanogrinding and ball milling using various solvent-free methods. Along with the synthesis of material, the studies include crystallographic and thermal analyses, stating thermal stability up to 340 °C. Also, it stabilized the excited state (f = 0.0405) and enhanced the photoluminescence properties (Φ = 14%, τavg = 8.9 ns) in crystalline HPPIT. To assess the function, HPPIT and HPPIS were converted into films at different concentrations, and the maximum lifetime (τavg) was 16.96 ns with a quantum yield (Φ) of 6.1%. This approach highlights the valorization of industrial elemental sulfur into a luminescent functional material via solvent-free mechanochemical synthesis, which represents a paradigm for sustainable optoelectronics aligned with the United Nations Sustainable Development Goals.