Gas adsorption at high pressures in porous solids is commonly quantified in terms of the excess amount adsorbed. Despite the wide spectrum of adsorbent morphologies available, the analysis of excess adsorption isotherms has mostly focused on microporous materials and the role of mesoporosity remains largely unexplored. Here, we present supercritical CO₂ adsorption isotherms measured at \(T=308\) K in the pressure range \(p=0.02{-}21\) MPa on three adsorbents with distinct fractions of microporosity, \(\phi_2\), namely a microporous metal-organic framework (\(\phi_2=70\)%), a micro-mesoporous zeolite (\(\phi_2=38\)%) and a mesoporous carbon (\(\phi_2<0.1\)%). The results are compared systematically in terms of excess and net adsorption relative to two distinct reference states–the space filled with gas in the presence/absence of adsorbent–that are defined from two separate experiments using helium as the probing gas. We discuss the inherent difficulties in extracting from the supercritical adsorption isotherms quantitative information on the properties of the adsorbed phase (its density or volume), because of the nonuniform distribution of the latter within and across the different classes of pore sizes. Yet, the data clearly reveal pore-size dependent adsorption behaviour, which can be used to identify characteristic types of isotherm and to complement the information obtained using the more traditional textural analysis by physisorption.

多孔固体中在高压下的气体吸附通常根据过量的吸附量进行量化。尽管可用的吸附剂形态范围广，但对过量吸附等温线的分析主要集中在微孔材料上，而介孔性的作用在很大程度上仍未得到探索。在这里，我们介绍了 在三种不同微孔率分别为\（\ phi_2 \）的吸附剂上 ，在压力（\ = p {0.02 {-} 21 \） MPa的压力\\（T = 308 \） K下测量的超临界CO ₂吸附等温线。，即微孔金属有机骨架（\（\ phi_2 = 70 \）％），微中孔沸石（\（\ phi_2 = 38 \）％）和中孔碳（\（\ phi_2 <0.1 \）％）。系统比较了相对于两个不同参考状态（存在/不存在吸附剂的情况下充满气体的空间）的过量吸附和净吸附的结果，这是通过两次使用氦气作为探测气体的独立实验定义的。我们讨论了从超临界吸附等温线中提取有关吸附相性质（密度或体积）的定量信息的固有困难，这是因为后者在不同孔径范围内和跨孔径的不均匀分布。然而，这些数据清楚地揭示了取决于孔径的吸附行为，该行为可用于识别等温线的特征类型，并补充使用更传统的通过物理吸附进行的质构分析所获得的信息。