Enhanced hydrophobic UiO-66 (University of Oslo 66) metal-organic framework with high capacity and selectivity for toluene capture from high humid air.

Metal organic frameworks (MOFs) are good absorbents that provide high specific surface area, modified pore surface and controllable pore size. The aim of this work is to prepare a MOFs material with good toluene adsorption property in the presence of water. In this paper, modified UiO-66 (University of Oslo 66) was successfully synthesized with polyvinylpyrrolidone (PVP) as structure-directing agent by a simple solvothermal method. The physical and chemical properties were obtained by a series of characterization instruments. Some missing-linker defect sites were observed on modified materials (defective UiO-66) and were known as the main active sites for toluene adsorption. The defective UiO-66 (PVP-U-0.5, 259 mg g-1) demonstrated 1.7 times toluene adsorption capacity of the pristine UiO-66 (151 mg g-1) when the PVP/Zr4+ ratio was 0.5. The interactions between toluene and UiO-66 and PVP-U-0.5 were assessed through the Henry's law constant (KH) and the isosteric adsorption heat (ΔHads), which indicated that stronger interaction between PVP-U-0.5 and toluene molecules. Moreover, PVP-U-0.5 displayed good adsorption capacity (84 mg g-1) at high relative humidity (70% RH). Water temperature programmed desorption experiments revealed that PVP-U-0.5 had more hydrophobic property, which provided a further possibility for practical application for the removal of toluene.