Measurement and interpretation of unary supercritical gas adsorption isotherms in micro-mesoporous solids

Abstract Gas adsorption at high pressures in porous solids is commonly quantified terms of the excess amount adsorbed. Despite wide spectrum adsorbent morphologies available, analysis isotherms has mostly focused on microporous materials and role mesoporosity remains largely unexplored. Here, we present supercritical CO 2 measured $$T=308$$ T = 308 K pressure range $$p=0.02{-}21$$ p 0.02 - 21 MPa three adsorbents with distinct fractions microporosity, $$\phi_2$$ ϕ 2 , namely a metal-organic framework ( $$\phi_2=70$$ 70 %), micro-mesoporous zeolite $$\phi_2=38$$ 38 %) mesoporous carbon $$\phi_2<0.1$$ < 0.1 %). The results are compared systematically net relative to two reference states–the space filled gas presence/absence adsorbent–that defined from separate experiments using helium as probing gas. We discuss inherent difficulties extracting quantitative information properties adsorbed phase (its density or volume), because nonuniform distribution latter within across different classes pore sizes. Yet, data clearly reveal pore-size dependent behaviour, which can be used identify characteristic types isotherm complement obtained more traditional textural by physisorption.