Hydrogen Isotope Separation within the Metal–Organic Framework Cu(I)-MFU-4<i>l</i>

Abstract

Hydrogen isotope separation within the metal–organic framework material known as Cu(I)-MFU-4l is investigated using a combination of breakthrough analysis, equilibrium measurements, and infrared spectroscopy. Results confirm the expected large infrared frequency shift of the adsorbed H2 vibrational mode and reveal an extremely high binding energy difference between H2 and D2 of 2.3 kJ/mol. Both static and dynamic measurements indicate that the material’s selectivity for D2 over H2 increases with decreasing temperature, reaching a maximum at ≈100 K, but then decreases for lower temperatures. These results indicate an activation barrier for the replacement of adsorbed H2 by D2 and place a limit on the material’s effectiveness for isotope separation at low temperature.