Modifications Of Cu-based Metal Organic Frameworks For Adsorption And Separation Of Hydrogen Isotope

Hydrogen isotopes,protium(1H),deuterium(2H or D),tritium(3H or T),play a key role in the medicinal chemistry,energy,nuclear industry,and in other fields.Hydrogen isotopes molecules have almost identical classical dimensions associated with very similar physicochemical properties,and the separation of hydrogen isotope mixtures in high purity has been considered as one of the greatest difficulties and challenges in modern separation technology.Although large-scale hydrogen isotope separation and enrichment has been achieved over the past few decades through processes such as low-temperature distillation,the process has high energy requirements and low separation factor.Therefore,other methods need to be explored to develop advanced isotope separation processes with low separation costs and high separation effects.In recent years,the quantum sieving effect has received extensive attention in hydrogen isotope separation.Suitable microporous materials are key to achieving the quantum sieving effect.Accordingly,based on the kinetic quantum effect(KQS)and chemical affinity quantum effect(CAQS),suitable metal organic framework or their composites are synthesized by using post-synthesis method,and are used to systematically study their adsorption capacity and selectivity for hydrogen isotopes mixtures through static/dynamic separation experiments.The main research contents are as follows:(1)Static adsorption of hydrogen isotopes by Pd-doped HKUST-1:Pd-doped HKUST-1 adsorbent with high Pd dispersion(Pd@HKUST-1-DS)was prepared by two-solvent method.The characterization show that the Pd nanoparticles are perfectly confined to the internal pores of HKUST-1,and the material has large physically structural parameters such as specific surface area and pore volume and strong metal-support interaction.Static adsorption experiments showed that the maximum absorption of H2 at 77 K and 2 bar(or 298 K and 18 MPa)was 3.72 wt.%(1.63 wt.%)and the maximum absorption of D2 at 77 K and 2 bar was 3.49 wt.%,respectively,which can be attributed to the large specific surface,pore volume and strong metal-support interaction.The analysis results show that compared with impregnated Pd/HKUST-1-IM,the Pd nanoparticles in Pd@HKUST-1-DS transfer more electrons to the HKUST-1 support,which enhances the metal-support interaction of the material with Pd nanoparticles,and improves the ability of the material to adsorb H2 and D2 at liquid nitrogen temperature and room temperature.This work provides an important example for the preparation of highly efficient adsorption hydrogen isotope materials.(2)Study on H2/D2 static separation on Cu+ modified HKUST-1:the Cu(Ⅰ)Cu(Ⅱ)-BTC with unique Cu(Ⅰ)and Cu(Ⅱ)coordination networks was synthesized.The material significantly facilitates D2/H2 isotope separation with a D2/H2 selectivity of 37.9 at 30 K due to the synergistic effect of KQS and CAQS.Density functional theory(DFT)calculations indicate that the introduction of Cu(Ⅰ)macrocycles in the framework decreases the pore size and further leads to relatively enhanced interaction of H2/D2 molecules on Cu(Ⅱ)sites,which improves the KQS and CAQS effects of Cu(Ⅰ)Cu(Ⅱ)-BTC.This work reveals the reasons for the counterintuitive behavior of Cu(Ⅰ)sites,which contributes to a deeper understanding of quantum sieving mechanisms and provides a new strategy for designing efficient isotope systems.(3)The study of H2/D2 dynamic separation hydrogen on HKUST-1 composites:MOF/zeolite composite(HKUST-1@silicate-1)was synthesized by in-situ hydrothermal method.The HKUST-1@silicate-1 could quickly separate 1:1 H2/D2 mixtures and did not lead to positive and secondary hydrogen due to CAQS induced by Cu2+ metal.In addition,the different components of ternary H2/HD/D2 mixtures can also be analyzed in HKUST-1@silicate-1.This work confirms the potential of HKUST-1@silicate-1 composites in the analysis of hydrogen isotopes of different components.