| Metal-organic frameworks（MOFs）have engaged great recognition in the field of hydrogen isotope H2/D2 separation because of their high porosity,variable structure.In this paper,two MOFs not reported in the literature are constructed by self-assembly reactions with transition metal ions（Ni/Co）using nitrogen-containing organic carboxylic acids 2,2’-bipyridine-3,3’-dicarboxylic acid-1,1’-N oxide and 4,4’-bipyridine containing multiple ligand sites as ligands.The crystal structures are resolved by single-crystal X-ray diffraction,characterized by IR,PXRD,TG-DTA,and elemental analysis,and the separation properties of the two complexes for the hydrogen isotope H2/D2 are investigated by a combination of theoretical calculations and experiments.The following research results are achieved:（1）The organic carboxylic acid 2,2’-bipyridine-3,3’-dicarboxylic acid-1,1’-N oxide and 4,4’-bipyridine are selected to react with Ni（NO3）2·6H2O to synthesize a MOF with the molecular formula[Ni（H2O）2Ni(C12H6N2O6)2(C10H8N2)2]·2H2O with a two-dimensional layered structure（Ni-MOF）.The single-crystal X-ray diffraction data indicate that the MOFs belongs to the orthogonal crystal system,P21212space group.The adsorption and separation selectivity of the hydrogen isotopes H2/D2 in Ni-MOF are simulated at different temperatures and pressures using the giant regular Monte Carlo simulation.The calculated results show that the maximum adsorption selectivity of Ni-MOF for D2/H2is 1.306 at 77 K,indicating that there is a chemical affinity quantum sieving effect of Ni-MOF for D2/H2.The diffusion coefficients of H2/D2 in Ni-MOF are calculated using molecular dynamics simulations,and the results show that the diffusion rate of H2 is faster than that of D2 at 20-77 K,so Ni-MOF exhibits kinetic selectivity for H2/D2,with a maximum kinetic selectivity of 1.57 at 20 K.The Ni-MOF@γ-Al2O3 composites with different Ni-MOF loadings are synthesized by liquid-phase epitaxy and used as chromatographic stationary phases to investigate the separation performance of the composites Ni-MOF@γ-Al2O3 for H2/D2 by gas chromatography at liquid nitrogen temperature（77 K）.The optimal H2/D2separation conditions are obtained by examining the loading of Ni-MOF,the carrier gas helium flow rate and the injection volume of H2/D2 mixture（1:1）.The results show that the optimized Ni-MOF loading of the composite material as the chromatographic stationary phase is able to achieve the separation of H2/D2.The results show that when the sample volume of H2/D2 mixture was controlled to be 100μL and the composite material with optimized Ni-MOF loading is used as the chromatographic stationary phase,and the carrier gas flow rate is set to 60 m L/min at this time,the resolution is 1.70 and the separation time is 4.84 min.And the stationary phase is also able to achieve the separation of H2/D2 at D2content of 10%.The RSD of chromatographic peak related parameters（peak height and peak area）are all below 5%,indicating that the stationary phase has good accuracy and reproducibility in the separation of H2/D2.（2）The organic carboxylic acids 2,2’-bipyridine-3,3’-dicarboxylic acid-1,1’-N oxide and 4,4’-bipyridine are selected to react with Co（NO3）2·6H2O to synthesize a MOF with the molecular formula[Co(C12H7N2O6)（C5H3N）]·2H2O（Co-MOF）with a three-dimensional open framework structure.The MOF is characterized by IR,PXRD,TG-DTA,and elemental analysis,and its single-crystal structure is resolved.The single-crystal results indicate that the MOFs belongs to the tetragonal crystal system,I41/acd space group.The adsorption and separation selectivity of hydrogen isotopes H2/D2 in Co-MOF are calculated using the giant regular Monte Carlo method at different temperatures and pressures,and the diffusion coefficients of H2/D2 in Co-MOF are calculated using molecular dynamics simulations.The results show that Co-MOF achieves separation of isotopic H2/D2 mainly based on the difference of H2/D2kinetic selectivity,with a maximum kinetic selectivity factor of 2.01 at 20K.Co-MOF@γ-Al2O3 composites with different Co-MOF loadings are prepared by liquid-phase epitaxy,and the separation performance of Co-MOF@γ-Al2O3 composites for H2/D2 is investigated by using them as chromatographic stationary phases.The optimal H2/D2 separation conditions are obtained by investigating the loading of Co-MOF,the carrier gas helium flow rate and the injection volume of H2/D2 mixture（1:1）.The resolution of the composite with H2/D2 is 2.73 and the separation time was 7.65 min when the composite material with optimized Co-MOF loading is used as the chromatographic stationary phase,and the He flow rate is set to 60 m L/min and the H2/D2（1:1）injection volume is 50μL.Even if the amount of D2 is reduced,the separation is still good.The RSDs of chromatographic peak-related parameters（peak height and peak area）are all below 5%,indicating that the stationary phase has good reproducibility in the separation. |
PDF Full Text Request