Quantum Sieving for Separation of Hydrogen Isotopes Using MOFs

Abstract

Hydrogen isotope mixtures can be separated either by confinement in small pores [i.e., "kinetic quantum sieving" (KQS)] or by strong adsorption sites [i.e., "chemical affinity quantum sieving" (CAQS)]. MOFs are excellent candidates for study of these quantum effects, due to their well-defined, tunable pore structures and the potential to introduce strong adsorption sites directly into the framework structure. In this microreview we summarize the recent status of hydrogen isotope separation using MOFs and future strategies relating to it. Fur-

Dynamic Studies on Kinetic H2/D2 Quantum Sieving in a Narrow Pore Metal–Organic Framework Grown on a Sensor Chip

“…Due to its high technical demand, the separation of deuterium from hydrogen still remains a challenging and industrially relevant task. Cryogenic methods for separation based on different boiling points of H 2 (20.3 K) and D 2 (23.6 K) give a selectivity of 3 at 20 K . The use of microporous materials offers a more efficient alternative method based on the quantum sieving (QS) effect.…”

“…Such small pores can be found in zeolites, carbon‐based materials, and metal‐organic frameworks (MOFs). Although many theoretical and computational investigations on QS have been performed, only a limited number of microporous materials have been tested for QS separation of H 2 /D 2 , such as zeolites, porous carbons, MOFs, and covalent–organic frameworks (COFs) …”

“…Cryogenic methods fors eparation based on different boilingp oints of H 2 (20.3 K) andD 2 (23.6 K) give as electivity of 3at20K. [1] The use of microporous materials offers amore efficient alternative method based on the quantum sieving (QS) effect.T his term, first introduced in 1995, describes ap henomenon appearing at low temperatures when the difference between the pore size and moleculard iameter of the adsorbate becomes comparable to the de Broglie wavelength of the adsorbate. [2] In this case, the heavieri sotope will have al ower zero-point energy,r esulting in its faster diffusionc ompared to the lighter isotope.…”

“…The different de Brogliew avelengths of H 2 and D 2 at 77 K(% 1.8 and 1.2 ,respectively) , [3] indicate asmaller molecular diameter for D 2 with respect to H 2 .W ith the molecular diameters of H 2 /D 2 estimated in the range of 2.4-3.1 , we can expect that QS might occur in ultramicropores with aperturew idths of < 5 ,a pproximately.S uch small pores can be found in zeolites, carbon-based materials, and metal-organic frameworks (MOFs). Although many theoretical and computationali nvestigations on QS have been performed, [4][5][6] only a limited number of microporous materials have been tested for QS separation of H 2 /D 2 , [1] such as zeolites, [7] porousc arbons, [3,8] MOFs, [9][10][11] and covalent-organic frameworks (COFs). [11,12] In most cases the H 2 /D 2 selectivity has been determined from the amounts taken up under certain (non)equilibrium conditions (i.e.f rom H 2 and D 2 adsorption isotherms or from desorption measurements on samples loaded with H 2 /D 2 mixtures).…”

A Promising Alternative for Sustainable and Highly Efficient Solar‐Driven Deuterium Evolution at Room Temperature by Photocatalytic D2O Splitting

“…To verify the quantumseparation mechanism and develop ideal adsorbent materialsf or deuterium evolution, numerouss tudies regarding KQS have been reported. [12] To our knowledge,t he highest experimentally recorded separation factor is 13.6 at 40 K, [13] which represents ab etter performance than conventionalc ryogenic distillation at 24 Kf or deuterium evolution, with as eparation factor of 1.5. [10] However,p utting aside the promising advantages of quantum sieving (QS) technology,t he separation mechanism exhibits significant selectivity only at cryogenic temperatures ( Figure 1a nd Ta ble 2), therebys till requiring substantial energy consumption, which presents practical scale-up application challenges.…”