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 D2, whereas no response is observed for H2 and HD. In situ neutron diffraction directly reveals this pressure-dependent phase transition. Low-temperature thermal desorption spectroscopy measurements indicate an outstanding D2-over-H2 selectivity of 11.6 at 23.3 K, with high D2 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 T2, demonstrating gate opening as a highly effective approach for isotopolog separation.
Bibliographical noteFunding Information:
The current study was funded by DFG within FOR2433 research unit ?MOF-switches.? V.B. thanks BMBF (project no. 05K19OD2) for financial support. J.D.E. is supported by a Ramsay Fellowship from the University of Adelaide. T.H. thanks DFG RTG2721 ?Hydrogen Isotopes.? ZIH Dresden and Phoenix HPC service at the University of Adelaide are thanked for providing high-performance computing resources.
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