A novel porous material capable of separating deuterium (D2) from hydrogen (H2) at a temperature of 120 K has been introduced. Notably, this temperature exceeds the liquefaction point of natural gas, thus facilitating large-scale industrial applications. This advancement presents an attractive pathway for the economical production of D2 by leveraging the existing infrastructure of liquefied natural gas (LNG) production pipelines. The research conducted by Ulsan National Institute of Science & Technology (UNIST), Korea, Helmholtz-Zentrum Berlin, Heinz Maier Leibnitz Zentrum (MLZ), and Soongsil University, Korea, has been published in Nature Communications.
Deuterium, a stable isotope of hydrogen, plays a critical role in enhancing the durability and luminous efficiency of semiconductors and display devices, as well as serving as a fusion fuel in energy production. However, the increasing demand for D2 presents challenges in its production, primarily due to the need to separate from hydrogen through a cryogenic distillation process conducted at temperatures as low as 20 K (-253°C). While research has explored the use of metal-organic frameworks (MOFs) for D2 separation, their efficiency diminishes significantly at elevated temperatures.
In this study, the research team presented a copper-based zeolite imidazolate framework (Cu-ZIF-gis), which shows exceptional D2 separation performance, even at 120 K (-153℃). While typical MOFs operate effectively at around 23 K (-250℃), their performance decreases sharply as temperatures approach 77 K (-196℃). However, the newly developed Cu-based MOF demonstrates a significant advantage in maintaining its effectiveness at higher temperatures.
For the first time, the research team identified that the superior performance of this material results from the increased expansion of its lattice as the temperature rises. At cryogenic temperatures, the pores of the developed MOF are smaller than H2 molecules, thereby inhibiting their passage. However, as the temperature increases, the lattice expands, leading to an increase in pore size. This enlargement facilitates the passage of gases through the pores, thereby enabling the separation of H2 and D2 via the quantum sieving effect, wherein heavier molecules traverse the pores more efficiently at lower temperatures.
Confirmatory in-situ X-ray diffraction (XRD) and quasi-elastic neutron scattering (QENS) experiments, conducted at the Institut Laue-Langevin (ILL) in Grenoble, France, by the joint team from UNIST, HZB and MLZ, confirmed the expansion of the lattice framework with increasing temperature, as well as the difference in isotope diffusivity even at elevated temperatures. Additionally, the analysis from the Thermal Desorption Spectroscopy (TDS) experiments indicated stable D2 separation at elevated temperatures.
Read more on HZB website
Image: The crystal structure of Cu-ZIF-gis that shows cylindrical straight channels along the c-axis. The pores were calculated with Connolly surfaces with a probe of 1.1 Å. (Cu, orange; N, blue; C, gray; O, magenta; H, white).
Credit: Minji Jung / Department of Chemistry, UNIST