Evaluation of MOF-based adsorbents for sampling and measurements of semi-volatile organic compounds (SVOCS) from contaminated air

Understanding the challenges of effectively capturing and analyzing semi-volatile organic compounds (SVOCs) from contaminated air is crucial for environmental monitoring. In this study, selected Zr-containing metal-organic frameworks (MOFs), UiO-67 and UiO-67-Ni, have been investigated for their potential on adsorption of a group of nonpolar SVOCs so called as poly-aromatic hydrocarbons (PAHs). Acenaphthene (Acp) was used as a model SVOC, and adsorption tests were investigated using the static headspace sampling technique, and desorption technique using methanol under ultrasonic conditions. Parameters including desorption time and adsorbent dosage have been investigated as independent variables for extraction performance, where the General Full Factorial design method has been applied for an experimental design. Comparing two different MOFs with same crystal structure and different pore size has demonstrated the exact effect of pore accessibility and interaction of host-guest molecules in adsorption of SVOC. The results showed superior sampling performance for UiO-67-Ni, with an adsorption capacity of 0.226 µg mg-1, representing a 47.8% improvement compared to UiO-67. The gas removal efficiency reached 17.45% for UiO-67-Ni, compared to 11.81% for UiO-67. A collective interpretation of the data from characterization techniques demonstrated that the presence of Ni in the framework substantially increased pore size and specific surface area, which positively impacted the adsorption performance of the MOF. The pronounced pore diameter difference between UiO-67 and UiO-67-Ni (22.4 Å to 25.3 Å), and the total surface area of 1450.5 m² g⁻¹ in the Ni-containing MOF, are the driving forces behind higher adsorption performance.