This review examines eco-friendly strategies for the synthesis of heterocyclic compounds through the application of green chemistry principles. Traditional synthetic routes often rely on hazardous reagents, toxic solvents, and energy-intensive processes, leading to environmental and safety concerns. In contrast, green approaches emphasize mild reaction conditions, non-toxic catalysts, renewable feedstocks, and energy-efficient techniques to reduce waste and enhance sustainability. Key methods discussed include catalysis, solvent-free and green solvent systems, biocatalysis, and the use of biomass-derived starting materials. The review also highlights applications of green heterocyclic synthesis in pharmaceuticals, materials science, and environmental remediation. By integrating these sustainable strategies, heterocyclic chemistry can advance toward safer, more efficient, and environmentally responsible production, providing a roadmap for future research and industrial practice.

Microfibers, particularly polyethylene terephthalate (PET, commonly known as polyester), are the predominant form of microplastic pollution in aquatic environments. However, the process by which PET microfibers form in these environments remains unclear. To investigate this, we exposed PET microfibers to both freshwater and seawater environments and subjected them to ultraviolet irradiation for 12 days. According to atomic force microscopy, X-ray photoelectron spectroscopy, differential scanning calorimetry, and gel permeation chromatography analyses, PET microfibers exhibited diverse photoaging behavior in freshwater and seawater environments, with the photoaging rate in seawater higher than in freshwater and ultrapure water. Photochemically active ions, including Cl^-, Br^-, and NO₃^-, are identified as the dominant factors controlling the aging rate of PET microfibers, particularly NO₃^-. Mechanistic insights suggest that this effect is due to the higher steady-state concentration of •OH produced in solutions containing these ions (6.04 × 10^-15 M for Cl^-, 4.93 × 10^-15 M for Br^-, and 8.00 × 10^-15 M for NO₃^-) compared to pure water (3.72 × 10^-15 M), which further accelerates PET photoaging. These findings provide an in-depth understanding of the formation and fate of PET microfibers in freshwater and seawater environments.