Highly effective hydrogen isotope separation through dihydrogen bond on Cu(I)-exchanged zeolites well above liquid nitrogen temperature

Abstract

Hydrogen isotope separation under moderate conditions with high selectivity remains a huge challenge due to the identical physicochemical properties of the isotopes. Here, we present zeolite materials with an excellent thermal stability and highly selective for hydrogen isotope separation through dihydrogen bond on ion-exchanged Cu(I) centers. Thermal desorption spectroscopy (TDS) measurements show that hydrogen isotope separation and enrichment can be carried out in a technologically favorable temperature range from liquid nitrogen temperature to near room temperature, and a D2/H2 selectivity of 24.9 for the Cu(I)-ZSM-5 zeolite is achieved, which is the highest selectivity value ever measured at 100 K. In addition, 99.6% of deuterium can be enriched through only three adsorption/desorption cycles from a mixture with a deuterium concentration of 2.5%. Structural characterization and density functional theory calculations reveal that the high hydrogen isotope selectivity of Cu(I)-ZSM-5 zeolite can be attributed to the strong chemical affinity through dihydrogen bond on Cu(I) sites with a large isotope effect in zero-point energy (ΔEZPE) and adsorption enthalpy (ΔH), resulting in hydrogen isotope separation and enrichment efficiently through low-cost materials in a technological scale.