Isotope-selective pore opening in a flexible metal-organic framework.

Bondorf, Linda; Fiorio, Jhonatan Luiz; Bon, Volodymyr; Zhang, Linda; Maliuta, Mariia; Ehrling, Sebastian; Senkovska, Irena; Evans, Jack D et al. · Sci Adv · 2022

basic_science · Level V

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Abstract

Flexible metal-organic frameworks that show reversible guest-induced phase transitions between closed and open pore phases have enormous potential for highly selective, energy-efficient gas separations. Here, we present the gate-opening process of DUT-8(Ni) that selectively responds to D<sub>2</sub>, whereas no response is observed for H<sub>2</sub> and HD. In situ neutron diffraction directly reveals this pressure-dependent phase transition. Low-temperature thermal desorption spectroscopy measurements indicate an outstanding D<sub>2</sub>-over-H<sub>2</sub> selectivity of 11.6 at 23.3 K, with high D<sub>2</sub> uptake. First-principles calculations coupled with statistical thermodynamics predict the isotope-selective gate opening, rationalized by pronounced nuclear quantum effects. Simulations suggest DUT-8(Ni) to remain closed in the presence of HT, while it also opens for DT and T<sub>2</sub>, demonstrating gate opening as a highly effective approach for isotopolog separation.