分子模拟研究微孔材料对光气吸附扩散性能的影响及材料筛选

利用分子模拟的方法研究了微量光气(COCl₂)在微孔材料中的吸附和扩散性能, 并分析了材料结构的影响. 结果表明, 光气在金属有机框架材料(MOF)和共价有机框架材料(COF)中的吸附等温线主要表现为第Ⅰ类型和第Ⅴ类型吸附. 当光气压力较低时, COF材料和含有开放金属位点的材料对其吸附性能较好. 通过对不同压力下吸附量的比较发现, 吸附达到饱和前, 随着压力和孔隙率(VF)的升高, 材料对光气的吸附量增大. 通过分子动力学模拟研究光气在微孔材料中的扩散性能发现, 较强吸附位点的存在不利于光气在孔道中的扩散. 通过气体分子在材料中的径向函数分布图及模拟轨迹分析发现, 分子协同效应和空间位阻效应相互竞争决定了扩散速率的快慢. 综合评价材料的吸附和扩散性能发现, COF-102, COF-300, ZnMOF-74, Zn-DOBDC和PCN-60是理想的吸附材料, 这些材料可以应用于环境中光气泄漏的防治.

Molecular Simulation Study on Influence and Screening of Micro-porous Materials for Phosgene Adsorption and Diffusion†

The adsorption and diffusion of phosgene(COCl₂) were calculated using molecular simulation in micro-porous materials. The influence of geometry of materials was still analyzed. The results show that the adsorption isotherms mainly are type Ⅰ and type Ⅴ in the researches. At low pressure the good performance of adsorption is covalent organic framework(COF) series and metal-organic framework(MOF) containing open-metal sites. Through the comparison of adsorption in different pressures, the adsorption capacity was determined by void fraction(VF) of materials with pressure increasing before reaching saturated adsorption. The strong adsorption site could obstruct the diffusivity of phosgene in micro-porous materials from molecular dynamic simulation. The diffusivity of phosgene is affected by competition between molecular synergy effects and steric effects through the analysis of radial distribution function(RDF) and molecular trajectory. It was found that COF-102, COF-300, ZnMOF-74, Zn-DOBDC and PCN-60 are good candidates for phosgene adsorption, which would be implemented in environment governance for capture of phosgene.