This review critically examines the dual nature of chlorine as both an indispensable base chemical and a potential risk. Chlorine and its by-product hydrogen chloride play essential roles in the production of pharmaceuticals, plastics, agrochemicals, and disinfectants. However, their inherent toxicity, risks of handling, and environmental impacts necessitate a reassessment of their use and sustainability. The review explores emerging and established chlorine-free technologies, such as the hydrogen peroxide to propylene oxide (HPPO) process and phosgene-free routes for polycarbonate production, evaluating their potential to reduce reliance on chlorine. For applications where chlorine remains indispensable, innovations such as trichloride- and bichloride-based Ionic Liquids provide safer storage and handling options for chlorine and hydrogen chloride, respectively. These Ionic Liquids not only enhance safety but also support renewable energy integration through their potential as indirect energy storage solutions. While chlorine is unlikely to be fully replaced in the near future, ongoing innovations in chlorine-free processes and safer technologies may redefine its industrial use, contributing to a more sustainable and secure chemical industry.
