One of the greatest challenges of modern separation technology is separating and purification of isotope mixtures. The separation of hydrogen isotopes, in particular, can generate significant economic value by yielding deuterium (D) and tritium (T), which are crucial for a variety of industrial and scientific applications. However, existing separation methods exhibit low efficiency due to the similar chemical properties of isotopes. In this study, we investigate two metal–organic frameworks (MOFs), Cu-ATC and Cu-bptc, composed of Cu²⁺ ions coordinated to 1,3,5,7-adamantanetetracarboxylate (ATC) and 3,3',5,5'-biphenyltetracarboxylate (bptc) linkers, respectively. Although the pore sizes of two MOFs are comparable, their pore structures differ substantially. Cu-bptc exhibits a cage-like structure, with window diameters of approximately 6 Å and cage diameters of around 10 Å. In contrast, Cu-ATC adopts a one-dimensional channel structure with a more compact distribution of open metal sites. Experimental data indicate that Cu-ATC demonstrates higher H2/D2 uptake at low pressures, with a significantly greater isosteric heat of adsorption (Qst) at initial adsorption compared to Cu-bptc. Simulations confirmed that the exposed Cu²⁺ ions in the copper paddlewheel structures serve as the primary binding sites for H2/D2 in both MOFs. The shorter Cu²⁺–Cu²⁺ distance in Cu-ATC (5.98 Å) enables one H2/D2 molecule to interact with two neighboring Cu²⁺ ions simultaneously, resulting in synergistic interactions. In contrast, one H2/D2 molecule in Cu-bptc interacts with only one single Cu²⁺ ion, leading to a weaker interaction and a significantly lower Qst at initial adsorption. Notably, Cu-ATC also exhibits superior efficiency in hydrogen isotope separation, as demonstrated by dynamic column breakthrough experiments conducted at atmospheric pressure and 77 K.

Metal–Organic Framework (MOFs), Hydrogen Isotope, Separation, Breakthrough Experiments