Molecular Sieving Properties of Nanoporous Mixed-Linker ZIF-62: Associated Structural Changes upon Gas Adsorption Application
Molecular Sieving Properties of Nanoporous Mixed-Linker ZIF-62: Associated Structural Changes upon Gas Adsorption Application
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DOI：
10.1021/acsanm.1c00010
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发表时间：
2021-03-19
影响因子：
5.9
通讯作者：
Silvestre-Albero, Joaquin
中科院分区：
文献类型：
--
作者：
Gandara-Loe, Jesus;Bueno-Perez, Rocio;Silvestre-Albero, Joaquin
评价分子筛咪唑骨架(ZIF)的柔韧性对于了解其在气体吸附和分离应用中的性能是非常有用的。在这里，我们用气体吸附测量、宏正则蒙特卡罗模拟和在Operando条件下的同步辐射X射线粉末衍射相结合的方法评价了纳米孔混合连接剂ZIF-62的吸附性能。虽然在77K和大气压下，纳米孔ZIF-62上的吸附研究预测了很大的O-2/N-2分离能力，但计算研究预计，观察到的差异必须归因于低温下N-2进入内部孔隙率的动力学限制。有趣的是，当吸附温度略有提高(90K比77K)时，N-2和O-2都能够通过促进气体吸附的相变(约3.8%的体积膨胀)进入内部孔结构。基于纳米孔ZIF-62在低温下对O-2/N-2具有优异的分子筛性能，我们将研究扩展到直链和支链碳氢化合物的吸附。本研究预测了小分子烃(C-2)在ZIF-62分子筛上优先吸附烷烃，而对于C-3及以上碳氢化合物，吸附过程主要受动力学限制。
The evaluation of the flexibility in zeolitic imidazolate frameworks (ZIFs) has been very useful to understand their performance in gas adsorption and separation applications. Here, we have evaluated the adsorption properties of a nanoporous mixed-linker ZIF-62 using a combination of gas adsorption measurements, grand canonical Monte Carlo simulations, and synchrotron X-ray powder diffraction under operando conditions. While adsorption studies in nanoporous ZIF-62 at 77 K and atmospheric pressure predict a large O-2/N-2 separation ability, computational studies anticipate that the observed differences must be attributed to kinetic restrictions of N-2 to access the internal porosity at cryogenic temperatures. Interestingly, upon a small increase in the adsorption temperature (90 K vs 77 K), both N-2 and O-2 are able to access the inner porous structure through the promotion of a phase transition (ca. 3.8% volume expansion) upon gas adsorption. This narrow phase (np) to expanded phase (ep) structural transition in ZIF-62 is completely suppressed above 150 K. Based on the excellent molecular sieve properties of nanoporous ZIF-62 for O-2/N-2 at cryogenic temperatures, we extended our study to the adsorption of linear and branched hydrocarbons. This study predicts the preferential adsorption of alkanes over alkenes in ZIF-62 for small hydrocarbons (C-2), while in the case of C-3 hydrocarbons and above, the adsorption process is mainly defined by kinetic restrictions.