柔性金属-有机骨架材料中甲醇吸附和扩散的分子模拟

Adsorption and Diffusion Characteristics of Methanol in the Flexible Metal-organic Framework Material Using Molecular Simulation

采用分子力学和分子动力学相结合的方法,对甲醇在Ni2(4,4'-bipyridine)3(NO3)4中的吸附能和扩散势垒进行了研究.结果表明,每个Ni2(4,4'-bipyridine)3(NO3)4结构单元的饱和吸附量是4个甲醇分子,稳定吸附分子个数是2个,吸附多于2个甲醇分子时材料结构变形明显,是甲醇实验吸附等温线出现梯级现象的原因,计算的扩散势垒是35.94kJ?mol-1,与实验值符合较好.得出,结构变形对吸附分子在柔性金属-有机骨架中的吸附和扩散性质有重要影响.

Adsorption energy and diffusion barrier of methanol in Ni2（4,4＇-bipyridine）3（NO3）4 were investigated using molecular mechanics and molecular dynamics method. The results indicated that each Ni2（4,4＇-bipyridine）3（NO3）4 unit can adsorb 4 methanol molecules and the structure was optimized for the uptake of 2 methanol molecules. The framework structure underwent obvious deformation when the loading was above 2, which resulted in methanol adsorption isotherm step. The calculated diffusion barrier （35.94 kJomol^-1） accorded with the experiment well. It could be concluded that structure deformation strongly affected the adsorption and diffusion characteristic of adsorbate in flexible metal-organic frameworks （MOFs）.