Fabrication of zeolitic imidazolate framework-8-methacrylate monolith composite capillary columns for fast gas chromatographic separation of small molecules

• Preparation of zeolitic imidazolate framework-8–methacrylate monolith composite capillary columns for gas chromatographic applications.
• Characterization of the prepared columns.
• Evaluation of the hydrodynamic properties and separation of a standard sample of alkanes and polar solvents as well as a gas sample.
• Investigation of the resolution and efficiency, as well as a comparison with an open tubular conventional column.
• Evaluation of the repeatability and stability of the prepared columns and separation of a real paint thinner sample.

A composite zeolitic imidazolate framework-8 (ZIF-8) with a butyl methacrylate-co-ethylene dimethacrylate (BuMA-co-EDMA) monolithic capillary column (33.5 cm long × 250 μm i.d.) was fabricated to enhance the separation efficiency of methacrylate monoliths toward small molecules using conventional low-pressure gas chromatography in comparison with a neat butyl methacrylate-co-ethylene dimethacrylate (BuMA-co-EDMA) monolithic capillary column (33.5 cm long × 250 μm i.d.). The addition of 10 mg mL−1 ZIF-8 micro-particles increased the BET surface area of BuMA-co-EDMA by 3.4-fold. A fast separation of five linear alkanes in 36 s with high resolution (Rs ≥ 1.3) was performed using temperature program. Isothermal separation of the same sample also showed a high efficiency (3315 plates m−1 for octane) at 0.89 min. Moreover, the column was able to separate skeletal isomers, such as iso-octane/octane and 2-methyl octane/nonane. In addition, an iso-butane/iso-butylene gas mixture was separated at ambient temperature. Comparison with an open tubular TR-5MS column (30 m long × 250 μm i.d.) revealed the superiority of the composite column in separating the five-membered linear alkane mixture with 4–5 times increase in efficiency and a total separation time of 0.89 min instead of 4.67 min. A paint thinner sample was fully separated using the composite column in 2.43 min with a good resolution (Rs ≥ 0.89). The perfect combination between the polymeric monolith, with its high permeability, and ZIF-8, with its high surface area and flexible 0.34 nm pore openings, led to the fast separation of small molecules with high efficiency and opened a new horizon in GC applications.