Abstract

Over the last fifty years, our society has relied heavily on per- and polyfluoroalkyl substances (PFAS), which enrich our lives through an extraordinary variety of applications, ranging from agriculture to electronics, including cosmetics, refrigerants, tools and textiles. However, their sourcing and use are unsustainable: the extraction of fluoride, for example, inflicts devastating damage on ecosystems. PFAS are designed for single-use applications and are difficult to recycle; once disposed of, they take decades to degrade into toxic compounds characterised by high mobility and biomagnification. This leads to widespread and persistent pollution, which is also linked to global warming and ozone depletion. Conversely, the chemical stability of PFAS could catalyse a virtuous, low-carbon paradigm and promote improved global health. However, realising this model makes recycling an unavoidable imperative.

The LOOP project pursues this paradigm by utilising photoreductive coatings capable of mineralising any type of PFAS into reusable fluoride using sunlight. This approach overcomes the limitations of traditional oxidative catalysts, which are only suitable for degrading PFAS with non-fluorinated functional groups and solely under ultraviolet radiation. The primary objective is to recover fluoride in real-world contexts, where the presence of organic contaminants and oxygen hinders the direct reduction of carbon-fluorine (C–F) bonds. To this end, LOOP will implement selective mineralisation of organic pollutants and PFAS through rigorous design of the kinetic and thermodynamic requirements within junctions between semiconductor and plasmonic materials. LOOP therefore aims for the efficient recycling of fluoride, with the aim of reducing dependence on unsustainable mineral resources and mitigating the global legacy of fluorocarbon pollution, whilst laying the essential knowledge base for the development of light-driven photoreduction systems, for both environmental remediation and industrial synthesis.