Zhang Kang, Nalaparaju Anjaiah, Chen Yifei, Jiang Jianwen
Department of Chemical and Biomolecular Engineering, National University of Singapore, 117576, Singapore.
Phys Chem Chem Phys. 2014 May 28;16(20):9643-55. doi: 10.1039/c4cp00739e.
A molecular simulation study is reported for biofuel purification in six zeolitic imidazolate frameworks (ZIF-8, -25, -71, -90, -96 and -97) with different functional groups. For pure ethanol and water, the predicted adsorption isotherms agree fairly well with experimental data. Hydrogen bonding has an important effect on the adsorption of ethanol and water. In hydrophilic ZIFs (ZIF-90, -96 and -97) with polar groups, adsorption capacities are higher than in hydrophobic counterparts (ZIF-8, -25 and -71). The atomic charges in symmetrically functionalized ZIF-8, -25, and -71 are found to have an indiscernible effect on adsorption, in remarkable contrast to asymmetrically functionalized ZIF-90, -96 and -97. For ethanol-water mixtures representing the biofuel, the selectivity of ethanol-water drops with increasing ethanol in mixtures. It is revealed that the selectivity is determined primarily by framework hydrophobicity as well as the cage size. Among the six ZIFs, ZIF-8 exhibits the highest selectivity. This simulation study provides a microscopic insight into the adsorption of ethanol and water in various ZIFs, reveals the significant role of functional groups in governing biofuel purification, and would facilitate the development of new nanoporous materials for high-efficacy liquid separation.
本文报道了一项关于在六种具有不同官能团的沸石咪唑酯骨架（ZIF-8、-25、-71、-90、-96和-97）中进行生物燃料净化的分子模拟研究。对于纯乙醇和水，预测的吸附等温线与实验数据相当吻合。氢键对乙醇和水的吸附有重要影响。在具有极性基团的亲水性ZIFs（ZIF-90、-96和-97）中，吸附容量高于疏水性对应物（ZIF-8、-25和-71）。研究发现，对称官能化的ZIF-8、-25和-71中的原子电荷对吸附的影响不明显，这与不对称官能化的ZIF-90、-96和-97形成显著对比。对于代表生物燃料的乙醇-水混合物，乙醇-水的选择性随混合物中乙醇含量的增加而下降。结果表明，选择性主要由骨架疏水性和笼尺寸决定。在这六种ZIFs中，ZIF-8表现出最高的选择性。这项模拟研究为各种ZIFs中乙醇和水的吸附提供了微观见解，揭示了官能团在生物燃料净化中的重要作用，并将有助于开发用于高效液体分离的新型纳米多孔材料。
