Porous organic polymers for the adsorption of fluorinated gases

Abstract

The development of advanced materials exhibiting self-assembling and selective adsorption properties for the capture of fluorinated gases (F-gases) has attracted substantial attention, driven by the urgent need to mitigate the impacts of climate change. For the use of these materials at an industrial scale, the preparation of these materials must be both effective and economically accessible. Porous Organic Polymers (POPs) represent a broad and versatile class of materials entirely constructed from organic building blocks linked through covalent bonds. Their intrinsic porosity, high surface area, and tuneable functionality, including both crystalline and amorphous structures, make them attractive for a wide range of applications. Some of these properties can facilitate strong and selective interactions with F-gas molecules. These advanced materials offer promising alternatives to support the circular economy initiatives in the refrigeration sector, as encouraged by the European Union. In this study, the adsorption equilibria of difluoromethane (R-32), pentafluoroethane (R-125), 1,1,1-tetrafluoroethane (R-134a), sulphur hexafluoride (SF₆), and nitrogen (N₂) were experimentally determined on four distinct POPs: RIO-55, RIO-23, RIO-20, and RIO-12. The experimental data were fitted using the Dual-Site Langmuir adsorption model to capture the diversity of adsorption behaviours observed in these systems. Furthermore, competitive selectivity for representative commercial blends, R-410 A, R-407C, and SF₆/N₂, was evaluated through Ideal Adsorbed Solution Theory (IAST) calculations. Among the materials investigated, RIO-55 demonstrated the highest selectivity, particularly under low-pressure conditions, due to its optimal balance between microporosity and mesoporosity. This intrinsic ionic character further enhances interactions, making it the most promising candidate for the selective capture of F-gases.