Enhance Hydrogen Isotopes Separation by Alkali Earth Metal Dopant in Metal-Organic Framework.

ABSTRACT

Kinetic quantum sieving (KQS) based on pore size and chemical affinity quantum sieving (CAQS) based on adsorption site are two routes of porous materials to separate hydrogen isotope mixtures. Alkali earth metals (Be, Mg, and Ca) were doped into UiO-67 to explore whether these metal sites can promote H2/D2 separation. Based on the zero-point energy and adsorption enthalpy calculated by density functional theory calculations, the Be dopant shows better H2/D2 separation performance than other alkali earth metal dopants and unsaturated metal sites in metal-organic frameworks based on CAQS. Orbital interaction strongly relates to the chemical affinity and further influences the D2/H2 selectivity. Moreover, the predicted D2/H2 selectivity of Be-doped sites (49.4) at 77 K is even larger than the best experimental result (26). Finally, the different dynamic behaviors of H2 and D2 on Be-doped UiO-67 indicate its strong H2/D2 separation performance via KQS.