Influence of Structural Determinants on Dihydrogen Adsorption and Isotopologue Separation in Nanoporous Metal-Organic Frameworks.

Efficient separation of dihydrogen isotopologues, particularly D, is critical for applications in nuclear energy technology and environmental sciences. Conventional methods, such as cryogenic distillation, are energy-intensive and provide limited selectivity (S ≈ 1.4). Here, we report a systematic evaluation of diverse MOFs with ultramicropores, open metal sites (OMS), and framework flexibility for D/H separation. Thermal desorption spectroscopy (TDS) and adsorption studies revealed that ultramicroporous MOFs enable preferential D adsorption via kinetic quantum sieving, while bimetallic Ni-MOF-74(Co) achieves high selectivity S = 52 at 77 K through OMS-driven chemical affinity quantum sieving. Flexible MOFs, [Cu(Pr-trz-ia)] and [Cu(Et-trz-ia)], show temperature-responsive cryogenic flexibility with selectivities of 1.4-2.3 at 77 K. These findings highlight structural design as the key to advancing dihydrogen isotopologue separation at practical temperatures.