Predictions of Stepped Isotherms in Breathing Adsorbents by the Rigid Adsorbent Lattice Fluid
Predictions of Stepped Isotherms in Breathing Adsorbents by the Rigid Adsorbent Lattice Fluid
复制标题
DOI：
10.1021/acs.jpcc.9b02977
复制
发表时间：
2019-06-13
影响因子：
3.7
通讯作者：
Brandani, Stefano
中科院分区：
文献类型：
--
作者：
Verbraeken, Maarten C.;Brandani, Stefano
在吸附剂分子存在下发生结构变化的吸附剂是一类有趣的新型材料，它可以在分离技术中提供更高的选择性、纯度和回收率。然而，迄今为止，由于缺乏一个简单、一致的热力学框架，它们在这种技术中的应用受到阻碍，该框架可以有效地描述和预测它们在一系列条件下的吸附行为。对于它们在多组分吸附质混合物中的行为尤其如此，因为实验数据有限且难以获得。在这里，我们展示了相对简单的刚性吸附剂晶格流体模型如何成功和准确地预测呼吸金属-有机框架MIL-53 （Al）在CO2和CH4存在下的阶梯等温线。呼吸跃迁的预测完全基于材料两种结构构型的不同密度及其相关的吉布斯能。通过考虑结构的渗透应力，可以很容易地将迟滞效应包括在内，这可以很容易地从晶格流体表达式中计算出来。该模型可以用最少的实验或模拟数据进行参数化，随后变得具有预测性，并且由于该模型起源于统计力学，因此不需要预先假设，例如langmuir型行为，这与现有的（半）经验模型相比具有很大的优势。本研究中显示的方法应该是通用的，也应该同样适用于其他柔性吸附剂。
Adsorbents that undergo structural changes in the presence of adsorbate molecules are an interesting new class of materials, which could offer enhanced selectivity, purity, and recovery in separation technology. To date, however, their application in such technology is hampered by the lack of a simple, consistent thermodynamic framework, which can effectively describe and predict their adsorption behavior under a range of conditions. This becomes especially true for their behavior in multicomponent adsorbate mixtures, for which experimental data are limited and cumbersome to obtain. Here, we present how the relatively simple rigid adsorbent lattice fluid model successfully and accurately predicts stepped isotherms in the breathing metal-organic framework, MIL-53 (Al), in the presence of CO2 and CH4. Breathing transitions are predicted solely on the basis of the different densities of the material's two structural configurations and their associated Gibbs energies. Hysteresis effects can easily be included by considering the structures' osmotic stress, which can be calculated readily from the lattice fluid expressions. The model can be parameterized with a minimum of experimental or simulated data, subsequently becoming predictive, and because the model has its origins in statistical mechanics, no prior assumptions, such as Langmuir-type behavior, are required, presenting a major advantage over existing (semi)-empirical models. The approach shown in this study should furthermore be generic and should equally well apply to other flexible adsorbents.