二元气体混合物在非均质金属有机骨架表面吸附选择性的从头计算,The Journal of Physical Chemistry C

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二元气体混合物在非均质金属有机骨架表面吸附选择性的从头计算
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2023-06-27 , DOI: 10.1021/acs.jpcc.3c02494
Kaido Sillar ₁ , Arpan Kundu ₂ , Joachim Sauer ₂

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对吸附位点晶格 (L-GCMC) 进行大正则蒙特卡罗模拟，以预测金属中三种二元混合物 CO ₂ /CH ₄、CO ₂ /N ₂和 CH ₄ /N ₂的吸附选择性–有机骨架Mg ₂ (dobdc)，也称为CPO-27-Mg或Mg-MOF-74。基于 L-GCMC 模拟的纯气体吸附数据，我们评估了 IAST 在由于吸附分子之间的大量相互作用和吸附位点的异质性而导致吸附相不理想的条件下的性能。CO ₂ /CH _4对CO₂吸附的选择性^{当主要是 Mg 2+}位点占据时，混合物在 298 K 和低于大气压下达到最大值 290 。对于CO ₂ /N ₂混合物，随着表面覆盖度的增加直至完成单层，CO ₂吸附选择性不断增加至800。这表明，对于该混合物，开放金属位点的选择性不是最高的，而是对于开放金属位点的选择性最高。吸附在连接位点上。与 L-GCMC 结果相比，对于低于大气压的 CO ₂ /CH ₄混合物以及几乎整个压力范围的 CO ₂ /N _{2 ，IAST 预测的选择性被低估}混合物。因此，如果吸附相不理想，则 IAST 预测的选择性不太准确，并且实际材料可能是比 IAST 预测的更好的气体分离吸附剂。

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Ab Initio Prediction of Adsorption Selectivities for Binary Gas Mixtures on a Heterogeneous Metal–Organic Framework Surface

Grand canonical Monte Carlo simulations on a lattice of adsorption sites (L-GCMC) are performed for prediction of adsorption selectivities for three binary mixtures, CO₂/CH₄, CO₂/N₂, and CH₄/N₂, in the metal–organic framework Mg₂(dobdc), also known as CPO-27-Mg or Mg-MOF-74. Based on L-GCMC simulated pure gas adsorption data, we evaluated the performance of IAST in conditions where the adsorbed phase is nonideal due to substantial interaction between adsorbed molecules and heterogeneity of adsorption sites. The selectivity for CO₂ adsorption from the CO₂/CH₄ mixture reaches the maximum of 290 at 298 K and at subatmospheric pressures when mainly the Mg²⁺ sites get populated. For the CO₂/N₂ mixture, with increasing surface coverage up to completing the monolayer, the CO₂ adsorption selectivity continuously increases up to 800. This shows that for that mixture, the selectivity is not the highest for the open metal sites but for adsorption on Linker sites. Compared to L-GCMC results, the selectivities predicted by IAST are underestimated for subatmospheric pressures for the CO₂/CH₄ mixture and for almost the full pressure range for the CO₂/N₂ mixture. Thus, IAST predicted selectivities are less accurate if the adsorbed phase is not ideal, and the real material can be a much better adsorbent for gas separation than predicted by IAST.

更新日期：2023-06-27

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