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<p>Sorption coolers show strong potential for ground-based physical experiments and space exploration in the sub-Kelvin temperature regime, with their performance critically dependent on the adsorption behavior of helium on selected adsorbents. While most previous studies have focused on activated carbon, the present work systematically investigates the helium adsorption behavior of three porous materials: metal–organic framework (MOF) HKUST-1, single-walled carbon nanotubes (SWCNT), and multilayer graphene (MLG), over a temperature range of 4 to 77&#xa0;K and a pressure range of 1 to 500&#xa0;kPa. Evaluation of several adsorption isotherm models indicates that the Brunauer–Emmett–Teller (BET) model most accurately captures adsorption characteristics of three materials. Experimental results reveal a pronounced temperature dependence. In the low-temperature domain (4 to 10&#xa0;K), adsorption capacity increases sharply with pressure; however, in the higher-temperature domain (20&#xa0;K and above), adsorption tends toward saturation. Moreover, the relative adsorption performance of the three materials varies significantly with both temperature and pressure. Under low-temperature, low-pressure conditions (1&#xa0;kPa, 4&#xa0;K), SWCNT exhibit the highest adsorption capacity (24.03&#xa0;mmol g<sup>-1</sup>), making them particularly well suited for low-pressure refrigeration applications. In contrast, MLG shows the most significant enhancement in adsorption at high pressures: at 6&#xa0;K, its isotherm exhibits a pronounced increase with pressure, indicating strong affinity for helium under high-pressure conditions. HKUST-1, by comparison, exhibits a lower overall adsorption capacity, likely due to limitations associated with its framework stability and pore occupancy behavior. These findings provide an experimental basis and theoretical support for the selection and optimization of adsorbents in low-temperature adsorption refrigeration systems.</p>

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Experimental Investigation of Helium Adsorption on HKUST-1, Single-Walled Carbon Nanotube, and Multilayer Graphene at 4 ~ 77 K and 1 ~ 500 kPa with BET Model Analysis

  • 期刊论文

  • 发表日期：

    2025年10月28日

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  • Zhijian Zhang,
  • Biao Yang,
  • Xiaotong Xi,
  • Yihan Tian,
  • Zhaozhao Gao,
  • Liubiao Chen,
  • Junjie Wang

摘要

Sorption coolers show strong potential for ground-based physical experiments and space exploration in the sub-Kelvin temperature regime, with their performance critically dependent on the adsorption behavior of helium on selected adsorbents. While most previous studies have focused on activated carbon, the present work systematically investigates the helium adsorption behavior of three porous materials: metal–organic framework (MOF) HKUST-1, single-walled carbon nanotubes (SWCNT), and multilayer graphene (MLG), over a temperature range of 4 to 77 K and a pressure range of 1 to 500 kPa. Evaluation of several adsorption isotherm models indicates that the Brunauer–Emmett–Teller (BET) model most accurately captures adsorption characteristics of three materials. Experimental results reveal a pronounced temperature dependence. In the low-temperature domain (4 to 10 K), adsorption capacity increases sharply with pressure; however, in the higher-temperature domain (20 K and above), adsorption tends toward saturation. Moreover, the relative adsorption performance of the three materials varies significantly with both temperature and pressure. Under low-temperature, low-pressure conditions (1 kPa, 4 K), SWCNT exhibit the highest adsorption capacity (24.03 mmol g-1), making them particularly well suited for low-pressure refrigeration applications. In contrast, MLG shows the most significant enhancement in adsorption at high pressures: at 6 K, its isotherm exhibits a pronounced increase with pressure, indicating strong affinity for helium under high-pressure conditions. HKUST-1, by comparison, exhibits a lower overall adsorption capacity, likely due to limitations associated with its framework stability and pore occupancy behavior. These findings provide an experimental basis and theoretical support for the selection and optimization of adsorbents in low-temperature adsorption refrigeration systems.