Exploring the Potential of Metal-Organic Frameworks for the Separation of Blends of Fluorinated Gases with High Global Warming Potential.

Abstract

The research on porous materials for the selective capture of fluorinated gases (F-gases) is key to reduce their emissions. Here, the adsorption of difluoromethane (R-32), pentafluoroethane (R-125), and 1,1,1,2-tetrafluoroethane (R-134a) is studied in four metal-organic frameworks (MOFs: Cu-benzene-1,3,5-tricarboxylate, zeolitic imidazolate framework-8, MOF-177, and MIL-53(Al)) and in one zeolite (ZSM-5) with the aim to develop technologies for the efficient capture and separation of high global warming potential blends containing these gases. Single-component sorption equilibria of the pure gases are measured at three temperatures (283.15, 303.15, and 323.15K) by gravimetry and correlated using the Tóth and Virial adsorption models, and selectivities toward R-410A and R-407F are determined by ideal adsorption solution theory. While at lower pressures, R-125 and R-134a are preferentially adsorbed in all materials, at higher pressures there is no selectivity, or it is shifted toward the adsorption R-32. Furthermore, at high pressures, MOF-177 shows the highest adsorption capacity for the three F-gases. The results presented here show that the utilization of MOFs, as tailored made materials, is promising for the development of new approaches for the selective capture of F-gases and for the separation of blends of these gases, which are used in commercial refrigeration.