Capture of pure toxic gases through porous materials from molecular simulations

In the last three decades, the air pollution is the main problem to affect human health and the environment in China and its contaminants include SO_2, NH_3, H₂S, NO₂, NO and CO. In this work, we employed grand canonical Monte Carlo simulations to investigate the adsorption capability of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) for these toxic gases. Eighty-nine MOFs and COFs were studied, and top-10 adsorption materials were screened for each toxic gas at room temperature. Dependence of the adsorption performance on the geometry and constructed element of MOFs/COFs was determined and the adsorption conditions were optimised. The open metal sites have mainly influenced the adsorption of NH₃, H₂S, NO₂ and NO. Especially, the X-DOBDC and XMOF-74 (X = Mg, Co, Ni, Zn) series of materials containing open metal sites are all best performance for adsorption of NH₃ to illustrate the importance of electrostatic interaction. Our simulation results also showed that ZnBDC and IRMOF-13 are good candidates to capture the toxic gases NH_3, H₂S, NO₂, NO and CO. This work provides important insights in screening MOF and COF materials with satisfactory performance for toxic gas removal.

近三十年来，空气污染是影响中国人类健康与生态环境的主要问题，其污染物包括二氧化硫（SO₂）、氨气（NH₃）、硫化氢（H₂S）、二氧化氮（NO₂）、一氧化氮（NO）以及一氧化碳（CO）。本研究采用巨正则蒙特卡洛（grand canonical Monte Carlo）模拟方法，探究了金属有机骨架（metal-organic frameworks, MOFs）与共价有机骨架（covalent organic frameworks, COFs）对上述有毒气体的吸附性能。本次研究共考察了89种MOFs与COFs材料，并在室温条件下针对每种有毒气体筛选出吸附性能排名前十的材料。本研究明确了吸附性能与MOFs/COFs的几何结构及构筑基元之间的依赖关系，并优化了吸附实验条件。开放金属位点主要影响NH₃、H₂S、NO₂及NO的吸附过程；尤为关键的是，含有开放金属位点的X-DOBDC与XMOF-74（X=Mg、Co、Ni、Zn）系列材料对NH₃均展现出最优吸附性能，这印证了静电相互作用的重要性。本研究的模拟结果同时表明，ZnBDC与IRMOF-13是捕获NH₃、H₂S、NO₂、NO及CO等有毒气体的优质候选材料。本研究为筛选具备优异有毒气体去除性能的MOFs与COFs材料提供了重要的理论参考与研究思路。