Insights into Specific Surface Area Assessed by Inverse Gas Chromatography and Manometric Gas Adsorption: A...

This study presents a critical comparison of the surface area (SSA) assessment using inverse gas chromatography (IGC) and manometric gas adsorption (MGA). Based on an analysis of 73 literature data pairs, it is demonstrated that IGC, with n-alkanes as a probe, may serve as a valuable complementary tool to the standard BET method. For macro-mesoporous materials with SSA values below 150 m2 g-1, IGC provides results that are qualitatively and quantitatively consistent with MGA. While close agreement was observed for macro-mesoporous samples, the current dataset suggests increased variability for solids with narrow mesopores or micropores. Further experimental studies are needed to fully establish the reliability of IGC for these complex pore structures, where steric hindrances and pore morphology often impede probe accessibility and govern the adsorption geometry, particularly as the current findings are constrained by a limited dataset. Furthermore, this study highlights a fundamental conceptual flaw in the fixed molecular area assumption, which is physically invalid. SSA values obtained from these techniques are apparent values rather than intrinsic material properties, as the effective molecular area of a probe molecule is highly sensitive to temperature, surface chemistry, and adsorption geometry. This work provides key insights into these limitations, emphasizing the necessity of accounting for the temperature dependence of the molecular area. Experimental procedures are not reviewed beyond the bare minimum required to understand methods and their limitations.