ENGINEERING MULTISCALE POROSITY AND ADSORPTION THERMODYNAMICS IN PAN–SILICA HYBRID NANOCOMPOSITES: LINKING SOL–GEL SYNTHESIS WITH SURFACE ENERGY HETEROGENEITY
Keywords:
PAN–SiO₂, sol–gel, hierarchical porosity, adsorption, TVFM, thermodynamicsAbstract
This study establishes the relationship between synthesis conditions, multiscale pore architecture, and adsorption thermodynamics in PAN–SiO₂ hybrid nanocomposites prepared via sol–gel routes. Based on adsorption isotherms of benzene, water, and nitrogen analyzed using BET, V–t, BJH, DFT, and the Theory of Volume Filling of Micropores (TVFM), a hierarchical micro–mesoporous structure was identified, with a specific surface area up to 236 m²/g and a total pore volume approaching 1.0 cm³/g, where micropores contribute up to ~95% of the total pore volume.
An optimal composition (PAN–SiO₂ ≈ 1:3) was found to provide maximum pore development due to the formation of interpenetrating polymer–inorganic networks. Water adsorption reaches 3.79 mmol/g, significantly exceeding benzene adsorption (~0.99 mmol/g), indicating the dominance of specific interactions such as hydrogen bonding. Thermodynamic analysis reveals pronounced surface energy heterogeneity, with differential heats of adsorption up to 110 kJ/mol (water) and 98.5 kJ/mol (benzene), and strongly negative entropy values (down to −147 J/mol·K), reflecting restricted molecular mobility within the pore structure.
The adsorption behavior follows a multistage mechanism involving micropore filling, cooperative interactions (for water), and capillary condensation. The results demonstrate that both pore structure and surface energetics can be effectively tuned through synthesis, highlighting the potential of PAN–SiO₂ hybrid nanocomposites for advanced adsorption and separation applications.
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