Isotopologue-induced structural dynamics of a triazolate metal-organic framework for efficient hydrogen isotope separation.

Efficient hydrogen isotope separation remains the biggest challenge due to the nearly identical physicochemical properties of H and D. Through in situ neutron powder diffraction and gas adsorption experiments, we investigate the hydrogen isotopologue-induced structural dynamics of the triazole-based metal-organic framework [Mn(ta)]. Gas loading induces a measurable lattice expansion, more pronounced for H than D, and two distinct adsorption sites are identified with a subtle but significant difference in the occupancy of H and D at 60 K. Cryogenic thermal desorption spectroscopy after exposure to a 1:1 isotope mixture reveals an exceptionally high D/H selectivity of 32.5 at 60 K. When exposed to a D/H mixture of 5:95, D enriches to 75% in a single cycle. Given the commercial availability of the ligand and the scalability of the dia-framework topology across divalent transition metals, upscaling for industrial-scale deuterium separation is a realistic prospect. Our results give crucial molecular-level insights into isotopologue-induced structural dynamics in triazolate-based MOFs and provide guidance for improvement of isotope separation materials.