M-MOF-74吸附分离H2/He混合物的分子模拟研究

为了探究有机金属框架MOF-74能否作为一种优良的固体吸附剂，分离H₂/He混合物中H₂，并达到提纯He的目的，采用分子模拟的手段研究了H₂、He及H₂/He混合物在M-MOF-74（M=Mg、Co、Ni、Cu、Zn）上的吸附性能及吸附机理。结果表明，在1 bar（1 bar=10⁵ Pa）压力和25℃条件下，纯H₂对纯He在Ni-MOF-74上的选择性达6.58，而Mg-MOF-74对H₂的吸附量最大，其值为0.19 mmol·cm^-3，为He吸附量的6.46倍。当H₂/He混合物的浓度发生变化时，对其在M-MOF-74上的吸附分离因子没有较大影响，说明浓度变化不会影响M-MOF-74上吸附位点容纳H₂和He的能力。吸附位点和吸附热分析表明，MOF-74上的金属离子未饱和位点能够显著增强其对H₂的吸附能力。其结果对判断M-MOF-74是否具有分离H₂/He混合物的潜力，以及定量分析MOFs金属未饱和位点对H₂/He混合物分离的贡献提供了一定的理论基础。

Molecular simulation study on adsorption and separation of H2/He mixtures by M-MOF-74

In order to explore whether the organometallic framework MOF-74 can be used as an excellent solid adsorbent to separate H₂ in H₂/He mixture and achieve the purpose of purifying He, the adsorption performance and adsorption mechanism of H₂, He and H₂/He mixture on M-MOF-74 (M=Mg, Co, Ni, Cu, Zn) were studied by molecular simulation. The results show that the selectivity of pure H₂ to pure He on Ni-MOF-74 is 6.58 under the conditions of 1 bar pressure and 25 °C. The amount of H₂ adsorbed on Mg-MOF-74 is the largest (0.19 mmol·cm^-3) in the same condition, which is 6.46 times of He. When the concentration of the H₂/He mixture was changed, it had no great effect on its adsorption separation factor on M-MOF-74, indicating that the concentration change would not affect the ability of the adsorption sites on M-MOF-74 to accommodate H₂ and He. The adsorption site and adsorption heat analysis showed that the metal ion unsaturated sites on MOF-74 could significantly enhance its adsorption capacity for H₂. The results provide a theoretical basis for judging whether M-MOF-74 has the potential to separate H₂/He mixtures and quantitatively analyzing the contribution of metal unsaturated sites of MOFs to the separation of H₂/He mixtures.