Adsorption Of Volatile Organic Compounds (VOCs) On Metal-Organic Frameworks MIL-101

Volatile organic compounds (VOCs) existed in ambient environment may bring on serious environmental and health risks including photochemistry smog. Metal-organic frameworks (MOFs) MIL-101 with extremely large pore volume and high surface area, is a highly potential candidate as adsorbent on gas adsorption. Therefore, the excellent MIL-101 was hydrothermally synthesized in this paper to examine its adsorption performance for VOCs and the influences of molecular properties such as size and shape of VOCs. Meanwhile, the influences of competition adsorption of water vapor and toluene towards benzene on MIL-101 was also investigated. All studies in this paper was aimed to provide some theoretical basis and technical support for the sorption and removal of VOCs contamination. The main results are as follows:1. MIL-101 shows superior adsorption capacity for acetone and BTEX. Adsorption of VOCs on MIL-101 is captured by a pore filling mechanism, showing the size and shape selectivity of VOC molecules into MIL-101 pores. These proves to be a negative linear relationship between the volume adsorption capacity of VOCs and their molecular cross-sectional area. Mostly, VOC molecules, such as acetone, benzene, toluene, ethylbenzene and p-xylene, enter into MIL-101 pores with the plane having the minimum diameter. However, m-xylene and o-xylene enter into the MIL-101pores with the plane having the maximum diameter because the two methyl groups, existing in o-xylene and m-xylene with an angle, blocked the pores with diameters smaller than their lengths.2. Competition of benzene by water molecules was observed on the surface of MIL-101, which lead to the decreasing of benzene adsorption capacity on MIL-101 with the increasing of relative humidity. At a relative humidity of 90%, adsorption capacity of benzene on MIL-101 is of 655 mg/g (68.6% of the benzene adsorption capacity on MIL-101 without water molecules), which implies that MIL-101 is a excenlent adsorbent in the application of VOC removal at relatively high humidity.3. Competition between benzene and toluene was also observed when they adsorbed onto MIL-101 simultaneously, showing that adsorption of benzene on MIL-101 decreased with the increasing of toluene concentrations. This competitive behavior can be well described by the ideal adsorption solution theory. In addition, mutually dissolved interaction between benzene and toluene both at relatively low concentrations may occur and result in the deviation of the prediction of the ideal adsorption solution theory from the experimental data.