The competitive and synergistic effect between adsorption enthalpy and capacity in D2/H2 separation of M2(m-dobdc) frameworks

Hydrogen isotope separation is a challenging task due to their similar properties. Herein, based on the chemical affinity quantum sieve (CAQS) effect, the D-2/H-2 separation performance of M-2(m-dobdc) (M = Co, Ni, Mg, Mn; m-dobdc(4)= 4,6-dioxido-1,3-benzenedicarboxylate), a series of honeycomb-shaped MOFs with high stability and abundant open metal sites, are studied by gases sorption and breakthrough experiments, in which two critical factors, gas uptake and adsorption enthalpy, are taken into consideration. Among these MOFs, Co(2()m-dobdc) exhibits the longest D-2 retention time of 180 min/g (H-2/ D-2/Ne: 1/1/98) at 77 K because of its second-highest adsorption enthalpy (10.7 kJ/mol for H-2 and 11.8 kJ/mol for D2) and the best sorption capacity (5.22 mmol/g for H-2 and 5.49 mmol/g for D-2) under low pressure of 1 kPa and 77 K), which make it a promising material for industrial hydrogen isotope separation. Moreover, the results indicate that H-2 and D-2 capacities under low pressure (about 1 kPa) dominate the final D-2/H-2 separation property of MOFs. (C) 2021 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.