Adsorption and Diffusion of Small Alcohols in Zeolitic Imidazolate Frameworks ZIF-8 and ZIF-90
Adsorption and Diffusion of Small Alcohols in Zeolitic Imidazolate Frameworks ZIF-8 and ZIF-90
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DOI：
10.1021/jp312489w
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发表时间：
2013-02-14
影响因子：
3.7
通讯作者：
Sholl, David S.
中科院分区：
文献类型：
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作者：
Gee, Jason A.;Chung, Jaeyub;Sholl, David S.
我们研究的吸附和扩散的小醇在ZIF-8和ZIF-90与相结合的实验和建模方法。我们的大正则蒙特卡罗（GCMC）模拟预测，这两个ZIF表现出轻微的吸附选择性乙醇甲醇，与以前的实验数据吻合得很好。发现在低压下醇的吸附吸收在ZIF-90中显著高于ZIF-8。我们的模拟表明，这是由于醇和ZIF-90的羰基之间的氢键，但这种效应不足以在吸附过程中引起ZIF-90骨架的明显柔性。我们还报告了醇的自扩散系数和Arrhenius参数测量脉冲场梯度NMR（PFG-NMR）和分子动力学（MD）模拟。使用PFG-NMR测量的扩散率表明，在T = 25 ℃下，甲醇相对于乙醇的扩散选择性在ZIF-8（S = 229）中显著高于在ZIF-90（S = 6）中。实验和模拟扩散率之间的定性协议，使用广义琥珀（GAFF）力场，包括框架的灵活性。
We examine the adsorption and diffusion of small alcohols in ZIF-8 and ZIF-90 with a combined experimental and modeling approach. Our Grand Canonical Monte Carlo (GCMC) simulations predict that both ZIFs exhibit a slight adsorption selectivity for ethanol over methanol, in good agreement with previous experimental data. The adsorption uptake of the alcohols at low pressures is found to be significantly higher in ZIF-90 than ZIF-8. Our simulations indicate that this is due to hydrogen bonding between the alcohols and the carbonyl group of ZIF-90 but that this effect is not strong enough to cause appreciable flexibility of the ZIF-90 framework during adsorption. We also report alcohol self-diffusivities and Arrhenius parameters measured using pulsed field gradient NMR (PFG-NMR) and molecular dynamics (MD) simulations. The diffusivities measured using PFG-NMR indicate that the diffusion selectivity of methanol over ethanol is significantly higher in ZIF-8 (S = 229) than in ZIF-90 (S = 6) at T = 25 degrees C. Qualitative agreement is obtained between experimental and simulated diffusivities using the generalized AMBER (GAFF) force field including framework flexibility.