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

Abstract Efficient hydrogen isotope separation remains the biggest challenge due to the nearly identical physicochemical properties of H2 and D2. 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)2]. Gas loading induces a measurable lattice expansion, more pronounced for H2 than D2, and two distinct adsorption sites are identified with a subtle but significant difference in the occupancy of H2 and D2 at 60 K. Cryogenic thermal desorption spectroscopy after exposure to a 1:1 isotope mixture reveals an exceptionally high D2/H2 selectivity of 32.5 at 60 K. When exposed to a D2/H2 mixture of 5:95, D2 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.