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Computational Study of ZIF-8 and ZIF-67 Performance for Separation of Gas Mixtures
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2017-08-11 00:00:00 , DOI: 10.1021/acs.jpcc.7b05700
Panagiotis Krokidas 1 , Marcelo Castier 1 , Ioannis G. Economou 1
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2017-08-11 00:00:00 , DOI: 10.1021/acs.jpcc.7b05700
Panagiotis Krokidas 1 , Marcelo Castier 1 , Ioannis G. Economou 1
Affiliation
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ZIF-67, a modification of ZIF-8 framework through Zn substitution with Co, is tested for the first time for the separation of ethylene/ethane mixture using molecular simulations. The framework consists of cages connected with narrow apertures, which exhibit flexibility through a swelling motion, allowing for relatively large penetrants to diffuse. ZIF-67 demonstrates an enhanced separation for the specific mixture. Various computational techniques are employed (conventional molecular dynamics and Monte Carlo simulations, umbrella sampling, and Widom particle insertion), and the separation mechanism is investigated in terms of sorption and diffusion, for both ZIF-8 and ZIF-67. The stiffer bonding of Co with the adjacent N atoms results in a tighter structure and an aperture with smaller size and lower swelling amplitude than ZIF-8. The diffusion results show a clear dependency of the kinetic-driven separation on the aperture flexibility of the different frameworks. The diffusivities of different sized molecules (from He to n-butane) are simulated in both ZIF-8 and ZIF-67 frameworks, and the molecular size is correlated with the aperture’s response variations. A generalized method based on these results is developed which helps the understanding of the sieving mechanism as a function of the penetrant size and of the aperture size and flexibility. This approach provides an efficient screening of modifiable frameworks toward more efficient separations.
中文翻译：
ZIF-8和ZIF-67分离混合气体性能的计算研究
ZIF-67是ZIF-8骨架的一种修饰，该修饰是通过用Co取代Zn进行的，使用分子模拟方法首次测试了分离乙烯/乙烷混合物的方法。该框架由与狭窄孔相连的笼子组成，这些孔通过膨胀运动表现出柔韧性，从而允许较大的渗透剂扩散。ZIF-67展示了特定混合物的增强分离效果。采用了各种计算技术（常规分子动力学和蒙特卡罗模拟，伞状采样和Widom粒子插入），并且针对吸附和扩散对ZIF-8和ZIF-67的分离机理进行了研究。与ZIF-8相比，Co与相邻N原子的刚性键合导致结构更紧密，孔径更小，溶胀幅度更低。扩散结果表明动力学驱动的分离对不同框架的孔径柔性有明显的依赖性。不同大小分子的扩散系数（从He到在ZIF-8和ZIF-67框架中都模拟了正丁烷，并且分子大小与孔径的响应变化相关。根据这些结果，开发出一种通用的方法，该方法有助于理解筛分机理与渗透剂尺寸以及孔尺寸和柔韧性的关系。这种方法可有效筛选可修饰的框架，以实现更有效的分离。
更新日期：2017-08-12
中文翻译：
ZIF-8和ZIF-67分离混合气体性能的计算研究
ZIF-67是ZIF-8骨架的一种修饰，该修饰是通过用Co取代Zn进行的，使用分子模拟方法首次测试了分离乙烯/乙烷混合物的方法。该框架由与狭窄孔相连的笼子组成，这些孔通过膨胀运动表现出柔韧性，从而允许较大的渗透剂扩散。ZIF-67展示了特定混合物的增强分离效果。采用了各种计算技术（常规分子动力学和蒙特卡罗模拟，伞状采样和Widom粒子插入），并且针对吸附和扩散对ZIF-8和ZIF-67的分离机理进行了研究。与ZIF-8相比，Co与相邻N原子的刚性键合导致结构更紧密，孔径更小，溶胀幅度更低。扩散结果表明动力学驱动的分离对不同框架的孔径柔性有明显的依赖性。不同大小分子的扩散系数（从He到在ZIF-8和ZIF-67框架中都模拟了正丁烷，并且分子大小与孔径的响应变化相关。根据这些结果，开发出一种通用的方法，该方法有助于理解筛分机理与渗透剂尺寸以及孔尺寸和柔韧性的关系。这种方法可有效筛选可修饰的框架，以实现更有效的分离。
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