The selective adsorption of CO₂ in mixture with other greenhouse gases by porous materials is challenging and it has several consequences from the environmental and economic point of view. We carried out DFT calculations with periodic boundary conditions and plane waves basis set to better understand the adsorption of CO₂, CO, CH₄, N₂, O₂, and H₂ within the pore of the metal-organic frameworks (MOFs) SIFSIX-2-Cu, SIFSIX-2-Cu-i, and SIFSIX-3-Cu. These porous materials have a copper ion coordinated to an organic linker and the inorganic SiF₆²⁻ pillar, and they show a remarkable CO₂ uptake. Our results show that the adsorption occurs preferentially close to the inorganic pillar SiF₆, which polarizes the gas molecule, increasing the electrostatic contribution to the interaction. The adsorption strength correlates with the size of the pore, and it is stronger in the smaller porous of SIFSIX-3-Cu for all gases. The successive loading of CO₂ in a T-shape form inside the porous indicates a synergic polarization effect, increasing the adsorption energy in SIFSIX-2-Cu and SIFSIX-2-Cu-i, but not in SIFSIX-3-Cu. For all materials, we observe the following order in the adsorption energy: CO₂ > CH₄ > CO > N₂ > O₂ > H₂, suggesting that a thermodynamic separation could be possible; however, kinetic effects are also important in SIFSIX-3-Cu.

Graphical abstract

中文翻译：

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通过计算研究调查MOF SIFSIX-2-Cu，SIFSIX-2-Cu-i和SIFSIX-3-Cu中的温室气体吸附。

多孔材料对与其他温室气体混合的CO ₂的选择性吸附具有挑战性，从环境和经济角度来看，它具有多种后果。我们进行了DFT计算与周期性边界条件和平面波基础集合，以更好地理解CO的吸附₂，CO，CH ₄，N ₂，O- ₂和H ₂的金属-有机骨架（MOF）的细孔内SIFSIX -2-Cu，SIFSIX-2-Cu-i和SIFSIX-3-Cu。这些多孔材料具有与有机连接基和无机SiF ₆ ^2-配位的铜离子，并显示出显着的CO ₂摄取。我们的结果表明，吸附优先发生在靠近无机柱SiF _6的位置，该极性使气体分子极化，从而增加了静电对相互作用的贡献。吸附强度与孔的大小有关，并且对于所有气体，在较小的SIFSIX-3-Cu孔中，吸附强度都更强。T形形式的CO ₂的连续加载表明了多孔内的协同极化效应，增加了SIFSIX-2-Cu和SIFSIX-2-Cu-i中的吸附能，但没有增加SIFSIX-3-Cu中的吸附能。对于所有材料，我们在吸附能上都遵循以下顺序：CO ₂  > CH ₄  > CO> N ₂  > O ₂  > H ₂，表明可以进行热力学分离；但是，动力学效应在SIFSIX-3-Cu中也很重要。

图形概要