UiO-66-coated hybrid micro-gas chromatography column chips: Evaluation of gas preconcentration and separation performances as a function of particle size, pore size, time, concentration, and flow rate

Metal-organic frameworks (MOFs) have been widely used as adsorbents for solid-phase microextraction and gas removal and as stationary phases for the chromatographic gas separation of various gaseous molecules, including hazardous volatile organic compounds (VOCs). Considering their potential as an adsorbent or a stationary phase for VOCs, we previously reported that a hybrid-functional micro-gas chromatography column chip (hybrid chip) fabricated using MOF-5 could perform gas preconcentration and separation in a single chip device. The previous study only addressed the feasibility of hybrid functions; this study evaluated the performance of the hybrid chips fabricated using four types of MOFs (MOF-5, MIL-125, UiO-66-Large, and UiO-66-Small). Each MOF-coated hybrid chip was evaluated for its preconcentration and separation performance for representative hazardous VOCs: benzene, toluene, ethylbenzene, and xylene (together known as "BTEX"). The experimental results showed that particle size and functional group drastically affect the preconcentration and separation performance, respectively. Finally, from the viewpoint of practical commercialization, repeatability and reproducibility tests were conducted to prove that the hybrid chip can be used as a pretreatment chip device for enhancing the sensitivity and selectivity of small gas analysis systems.