The Characterization of Two Metal-Organic Complexes Investigated by Spectroscopy, Electron Microscope and Thermogravimetric Analysis and Their Adsorption Behaviour for Polycyclic Aromatic Hydrocarbons

The classification of metal-organic framework (MOFs) is presently restricted to a few classical structures of MOFs for solid-phase extraction of polycyclic aromatic hydrocarbons (PAHs). However, separation of a similar construction of analytes and selectivity are not satisfactory using these MOFs in many cases. In the work presented herein, aminoisophthalic was selected as the ligand and copper ion and zinc ion as the subjects to prepare two metal-organic frameworks ([Zn(C₈NH₅O₄)(H₂O)] and [Cu(C₈H₆NO₄)₂(H₂O)]) by the hydrothermal synthesis method. Adsorption capacity, adsorption behavior and adsorption selectivity of two MOFs were studied for ten PAHs. The results indicate that ① the equilibrium adsorption capacity for PAHs are >30 mg/g and adsorption rates are >75%. The highest selectivity of two as-prepared MOFs reached 11.4, exceeding the classical MOF-5 (α_ij=10.9). Adsorption of PAHs on two as-prepared MOFs could be well described by the pseudo-second order kinetic model, with correlation coefficients R² of 0.9179-0.9995. The PAHs adsorption behavior of two MOFs is in accord with the Langmuir model and Freundlich equation with correlation coefficients R2 of 0.8452-0.9993. ② The shapes of [Zn(C₈NH₅O₄)(H₂O)] and [Cu(C₈H₆NO₄)₂(H₂O)] are rod and bulk respectively, with homogeneous distribution from evidence of scanning electron microscopy, X-ray Photoelectron Spectroscopy and Infrared Spectroscopy. Specific surface areas of [Zn(C₈NH₅O₄)(H₂O)] and [Cu(C₈H₆NO₄)₂(H₂O)] are 20.392 m²/g and 7.44 m²/g, respectively. Adsorption capacity of [Zn(C₈NH₅O₄)(H₂O)] is better than }. Comparatively, [Zn(C₈NH₅O₄)(H₂O)]n can be applied as the material for pre-concentration of PAHs and [Cu(C₈H₆NO₄)₂H₂O] as the packing column material for separation of PAHs.