Quantum Sieving for Separation of Hydrogen Isotopes Using MOFs

Hydrogen isotope mixtures can be separated either by confinement in small pores [i.e., kinetic quantum sieving (KQS)] or by strong adsorption sites [i.e., chemical affinity quantum sieving (CAQS)]. MOFs are excellent candidates for study of these quantum effects, due to their well-defined, tunable pore structures and the potential to introduce strong adsorption sites directly into the framework structure. In this microreview we summarize the recent status of hydrogen isotope separation using MOFs and future strategies relating to it. Furthermore, a state-of-the-art technique for the direct measurement of selectivity with regard to isotope mixtures is introduced. Experimental results relating to separation factors with different pore apertures in the case of KQS and the role of open metal sites in that of CAQS as a function of temperature and gas pressure are given. Furthermore, technologically relevant parameters such as feasible operating pressure and temperature are discussed with respect to possible applications in a temperature swing process.