Soft and diffusion-controlled Sr-MOF for efficient separation of H2O/D2O

Heavy water (D 2 O) electrolysis is the primary technology for D 2 production, playing an irreplaceable role in fields such as nuclear fusion research and isotope tracing. However, the inherent similarity in chemical properties between H 2 O and D 2 O (with only a 1.4 °C difference in boiling points) poses significant challenges to their separation. Furthermore, the extremely low natural abundance of D 2 O (0.015 %) increases the difficulty and cost of separation, while traditional electrolysis and distillation techniques are highly energy intensive. Therefore, there is an urgent need to develop novel adsorbents for efficient and environmentally sustainable H 2 O/D 2 O separation. Herein, we used polydentate ligand 2, 5-dihydroxyterephthalic acid (DOBDC) and its derivatives 4,4́-(anthracene-9,10-diyl) bis (2-hydroxybenzoic acid (ABHB) as raw materials to prepare two novel high coordination Sr-MOFs namely IPE-1 and IPE-2, respectively. These MOFs were applied for efficient separation of H 2 O and D 2 O at room temperature. X-ray diffraction results reveal that one Sr atom in IPE-1 is coordinated with 9 oxygen atoms. This high coordination number results in the formation of ultra-small rectangular pores of approximately 2.5 Å. Adsorption isotherms of N 2 , CO 2 , H 2 O, and D 2 O indicate that the ultramicroporous structure of IPE-1 precludes efficient diffusion of CO 2 and H 2 O molecules into the MOF channels. In contrast, the activated IPE-2 exhibits good CO 2 , H 2 O, and D 2 O uptake capacities of 3 mmol/g, 8.38 mmol/g, and 6.51 mmol/g at 298 K, respectively. The Q st values and K sap values of H 2 O and D 2 O indicate that the adsorption rates of H 2 O were much higher than D 2 O under 0.2 < P/P 0  < 0.7, with a calculated ratio of approximately 1.26. This study not only provides appealing MOFs materials for efficient H 2 O/D 2 O separation at room temperature but also provides a new avenue for preparing adsorbents with high stability and high separation performance.