Ethanol/ethyl acetate azeotropic mixture gas-phase separation using MOF-801-modified monolithic columns

Organic monolithic columns have traditionally been used for macromolecule separations; however, enhancing their performance for small molecule and azeotrope separations remains challenging. Incorporating particles into monolithic matrices has emerged as a promising strategy to overcome these limitations, particularly in gas chromatography (GC). In this work, a composite monolithic column comprising a minimal loading (0.2 wt%) of zirconium-based MOF-801 particles embedded within a divinylbenzene (DVB) polymer framework was successfully fabricated and evaluated under low operating pressure (0.2 MPa). The short 15 cm × 0.25 mm i.d. MOF-801@DVB columns enabled rapid, high-efficiency separation of light hydrocarbons, achieving sub-minute separation of linear alkane mixtures with excellent repeatability (RSD% 0.38-1.16 %) over ten injections and operational stability across >2000 runs. Thermodynamic characterization revealed that MOF-801 incorporation enhanced the dispersive surface energy of the monolith while maintaining high permeability. McReynolds constants confirmed a polar interaction character, and a clear enthalpy-entropy compensation behavior was observed during adsorption. The monolith demonstrated successful separation of ethanol/ethyl acetate azeotropic mixtures, achieving a selectivity of 8.3 at 120 °C, surpassing benchmark materials like ZIF-8. Zero-coverage enthalpy analysis indicated stronger guest-host interactions in the MOF-801@DVB system, attributed to enhanced dispersion forces and hydrophilic framework effects. In addition, inter-batch reproducibility across three independently prepared columns was confirmed (RSD% 1.41-6.29 %), demonstrating the reliability of the fabrication approach. This study underscores the potential of integrating MOF particles into organic monolithic matrices to expand their application in small molecule GC separations, providing a cost-effective, high-stability platform for rapid gas-phase separations driven by thermodynamic control.