Enhance Hydrogen Isotopes Separation by Alkali Earth Metal Dopant in Metal–Organic Framework

Abstract

Kinetic quantum sieving (KQS) based on pore size and chemical affinity quantum sieving (CAQS) based on adsorption site are two routes of porous materials to separate hydrogen isotope mixtures. Alkali earth metals (Be, Mg, and Ca) were doped into UiO-67 to explore whether these metal sites can promote H 2 /D 2 separation. Based on the zero-point energy and adsorption enthalpy calculated by density functional theory calculations, the Be dopant shows better H 2 /D 2 separation performance than other alkali earth metal dopants and unsaturated metal sites in metal−organic frameworks based on CAQS. Orbital interaction strongly relates to the chemical affinity and further influences the D 2 /H 2 selectivity. Moreover, the predicted D 2 /H 2 selectivity of Be-doped sites (49.4) at 77 K is even larger than the best experimental result (26). Finally, the different dynamic behaviors of H 2 and D 2 on Be-doped UiO-67 indicate its strong H 2 /D 2 separation performance via KQS.

Recent Progress in Functional Nanomaterials towards the Storage, Separation, and Removal of Tritium

“…[58] Kim et al reported a highly effective hydrogen isotope separation system based on MOF-74-IM-Ni 2+ by implementing the strategy of combining KQS and CAQS for the first time. [13] To date, hydrogen isotope separation based on CAQS has been studied in different kinds of MFU-4l, [60] Hofmann-type, [63] and (Be, Mg, and Ca)-doped [64] MOFs, which have shown excellent selectivities of D 2 -over-H 2 above liquid nitrogen temperatures. Recently, metal-ion-exchanged zeolites such as Cu(I)-ZSM-5, [56] Ag(I)-ZSM-5, [25] and Ag(I)-exchange zeolite Y [57] have been investigated for their excellent potential for hydrogen ion separation based on CAQS.…”

“…[14,16] Extremely high energy consumption, high cost, complex operational procedures, and low selectivity/separation factors are the main limitations of existing isotope separation technologies such as cryogenic distillation, [50] Girdler sulfide processing, [51] and thermal cycling absorption processes (TCAPs). [52] To develop a promising alternative method for separating hydrogen isotopes, several experimental and molecular simulation (MS) studies have revealed that various functional porous materials such zeolites, [15,25,33,[53][54][55][56][57] metal organic frameworks (MOFs), [8,9,13,14,[58][59][60][61][62][63][64] covalent organic frameworks (COFs), [65] nanoporous carbons, [66,67] metal organic cages, [68] and porous organic cages [69] exhibiting high porosity, ultrasmall pores, and diverse functionalities can selectively capture and separate hydrogen isotopes by relying on "quantum sieving" (QS). In porous materials such as zeolites and MOFs, hydrogen isotopes separation can be realized with high selectivity through "kinetic quantum sieving" (KQS) and "chemical affinity quantum sieving" (CAQS).…”

“…In porous materials such as zeolites and MOFs, hydrogen isotopes separation can be realized with high selectivity through "kinetic quantum sieving" (KQS) and "chemical affinity quantum sieving" (CAQS). [8,9,[13][14][15]25,33,[53][54][55][56][57][58][59][60][61][62][63][64] Metal-organic frameworks (MOFs) (e.g., MFU-4l; [59] MIL-53(Al); [61] and Fe-, Co-, and Ni-MOF-74 [58] ), constructed using ligands and metal nodes or clusters, have been extensively studied by various research groups for successful and efficient separation of hydrogen isotopologues owing to their unique properties such as high specific surface areas, well-defined tunable pore structures, structural diversity, high concentration of open metal site (OMS), and the potential to introduce strong adsorption sites to frameworks. KQS [9,61] and CAQS [13,58,60] are the well-proposed separation mechanisms in MOF, based on which D 2 -over-H 2 selectivities in excess of 10 have been reported.…”

“…In porous materials such as zeolites and MOFs, hydrogen isotopes separation can be realized with high selectivity through “kinetic quantum sieving” (KQS) and “chemical affinity quantum sieving” (CAQS). [ 8,9,13–15,25,33,53–64 ]…”

Non-Covalent Isotope Effects

“…Deuterated solvents serve as the source of deuterium in the synthesis of next generation OLEDs. The separation of H 2 and D 2 on metal organic frameworks (MOFs) has been recently gaining both theoretical and experimental attention. − Although a plethora of applications of perdeuterated materials emerge in the area of medicine and the design of new materials, in the latter case, the isotopic substitution of heavy atoms may need to develop even faster, as exemplified by the isotopic effect of heat dissipation in the nanomaterial realm. In this area, nontraditional methods of isotopic enrichment seem to be on the way to rapid development.…”