Ethanol and ethyl acetate are two industrially significant organic solvents, widely utilized across the pharmaceutical, food, biofuel, coatings, adhesives, and chemical manufacturing sectors [1,2]. Ethanol is often produced via fermentation or petrochemical synthesis, during which ethyl acetate can be generated as a byproduct through esterification reactions between ethanol and acetic acid under acidic or catalytic conditions [3]. Moreover, both solvents, such as extraction systems, flavorings, and cleaning agents, are commonly used in industrial formulations. Consequently, either intentionally or unintentionally, ethanol and ethyl acetate frequently coexist in process streams or product mixtures. Due to their similar physicochemical properties, particularly their close boiling points (78.4 °C for ethanol and 77.1 °C for ethyl acetate), they readily form a minimum-boiling azeotropic mixture, rendering their separation via conventional distillation highly challenging and energy-intensive [4,5]. This industrial need for selective and energy-efficient separation technologies motivates the exploration of advanced methods for effectively resolving ethanol/ethyl acetate mixtures.

Monolithic columns have emerged as a versatile alternative to traditional packed columns, offering high permeability, mechanical robustness, and tunable porosity. Since their introduction in the early 1990s [6]. Monolithic materials have been developed in both organic-based and inorganic-based formats, with organic polymer monoliths gaining particular attention due to their ease of fabrication, chemical stability, and surface functionalization flexibility [7].

While monolithic columns have found widespread application in liquid chromatography, their use in gas-phase separations remains comparatively less common. Challenges such as lower thermal stability for certain polymeric systems and difficulties in ensuring sufficient small-molecule interaction sites have historically limited their broader adoption in gas chromatography [[8], [9], [10]]. Nevertheless, developing monolithic columns for gas-phase separations remains of significant interest. This is particularly valuable because monolithic columns provide high permeability and low back-pressure, enabling fast GC on short column lengths without specialised hardware, which makes them attractive platforms for rapid gas-phase screening and thermodynamic parameter extraction. Such work can serve both analytical purposes, providing rapid and efficient methods for vapor-phase analysis, and as proof-of-concept platforms for designing advanced separation materials with potential industrial applications in areas such as solvent recovery, hydrocarbon fractionation, and azeotrope separation.

Among the various organic monoliths developed, divinylbenzene (DVB) monolithic columns have attracted considerable attention due to their relatively high thermal stability and mechanical robustness, making them promising candidates for gas chromatographic applications [11]. However, monolithic polymers inherently possess low surface areas, which limits their effectiveness in separating small molecules such as gases and volatile organic compounds (VOCs).

To address this limitation, several studies have developed DVB-based monolithic columns with exceptional separation performance, demonstrating the feasibility of fast and efficient gas-phase separations. Nevertheless, such improvements have often come at the cost of requiring very high operating pressures, sometimes exceeding several megapascals, which necessitates the use of specialized, customized GC systems [11,12]. This technical barrier restricts the broader adoption of high-performance DVB monoliths in standard GC applications, underlining the need for alternative strategies to enhance their performance at lower operational pressures.

To address this limitation, composite monolithic columns have been introduced, where the incorporation of nano- or microparticles into the polymer matrix significantly enhances the surface area, pore structure, and adsorption capacity [13,14]. Incorporating inorganic particles improves the ability to separate small molecules by increasing micropore density and creating more active interaction sites. Examples of such composite stationary phases include silica@monoliths [15,16], carbon nanotube@monoliths [[17], [18], [19]], and various hybrid organic-inorganic systems [[20], [21], [22], [23], [24]].

Within this framework, metal-organic frameworks (MOFs) have emerged as promising candidates for enhancing monolithic columns. MOFs are highly porous, crystalline materials characterized by enormous surface areas, tunable pore architectures, and rich chemical functionalities [25,26]. These features make them ideal candidates as stationary phases for chromatography, offering opportunities for selective interactions based on molecular size, shape, polarity, or polarizability [27,28].

Recent studies have demonstrated the application of MOFs in gas chromatography, either as packed columns, coated open tubular (OT) columns, or integrated into monolithic structures [29,30]. Among these configurations, composite MOFs@monolithic columns represent an emerging class of materials that combine the mechanical and permeability advantages of polymer monoliths with the adsorption selectivity of MOFs [[31], [32], [33], [34]].

In this context, MOF-801, a zirconium-based MOF featuring a fcu topology, presents particularly attractive properties for chromatographic applications. MOF-801 possesses hydrophilic pores, high thermal stability, and accessible microporosity (∼7.4 Å octahedral cages interconnected by 4.6–6.0 Å windows) [35]. These features offer a unique combination of selective adsorption behavior, robustness, and compatibility with polymerization processes.

While MOF-801 has been applied in gas storage [36,37], water adsorption [38,39], and selective gas separations [40,41], its application in chromatography, particularly in small molecule gas-phase separations, remains underexplored.

In this work, we report the fabrication of a MOF-801@DVB composite monolithic column via a straightforward in-situ polymerization method incorporating a minimal amount of MOF-801 particles (0.2 wt %). The resulting monolithic column operates under relatively low pressures, leveraging the high permeability of the DVB skeleton. A comprehensive chromatographic evaluation was conducted, including the separation of linear and branched alkanes, polarity assessment via McReynolds constants, and detailed thermodynamic investigations.

The adsorption behavior and physicochemical properties of the composite were systematically studied using pulse inverse gas chromatography (IGC) at infinite dilution. This thermodynamic analysis not only elucidated the surface energy characteristics and guest–host interactions of the monolithic structure but also provided critical insights into the separation of ethanol and ethyl acetate, a challenging azeotropic system. Furthermore, the composite’s stability, repeatability, and inter-batch reproducibility were thoroughly examined, highlighting its potential as a cost-effective, durable, and efficient stationary phase for advanced gas-phase separations.