Synthesis And Adsorption Property Of A Novel Chromium-Based Metal-Organic Framework

MIL-101is a prominent example of a new class of meso-or nano-porous materials,known as Metal-Organic Frameworks （MOFs）. Because of its extra large specific surface area,MIL-101has a great potential for applying in various fields. However, due to its low yield andhigh adsorption capacity for water, the application of MIL-101has been limited. Thisdissertation is just focused on these two problems.A new method of process improvement on the synthesis of MIL-101was advanced. Theeffects of different additives and the amount of additives on the synthesis of MIL-101, thephysical properties of the as-synthesized materials, including crystal structure, surfacemorphology and porous texture, as well as on the were investigated. Results showed that byadding1.5mmol NaF, the yield of as-synthesized MIL-101could reach69.7%, and this resultis20%higher than the yield of MIL-101synthesized following traditional synthesizingprocess. The improving of yield helps to save resource and energy as well as provide technicalsupport for furthering the application of MIL-101.A novel chromium-based MOF material, SCUT-1, was designed and successfullysynthesized. The effects of synthesis conditions were systematically investigated. Thepossibility of using microwave assistant method as alternative method to synthesize SCUT-1was also studied. Results showed that under the hydrothermal condition, the optimalsynthesizing conditions included Cr（NO₃）₃9H₂O/H₂NDC molar ration was1:1, the reactiontemperature was210℃, the reaction time was10h. Comparing with crystals synthesizedusing microwave assistant method, crystals synthesized by hydrothermal method showed abetter crystallinity, a regular morphology, and a higher specific surface area.Adsorption equilibrium and kinetics of water on the MIL-101and SCUT-1crystals werestudied. Water adsorption isotherms and kinetic curves were measured using gravimetricmethod. Results showed that under the same temperature, the amount adsorbed of water onthe SCUT-1crystals accounted for only a quarter of that on the MIL-101crystals. This revealsthat SCUT-1has a higher hydrophobicity.Adsorption equilibrium and kinetics of ethyl acetate on the MIL-101and SCUT-1 crystals were studied. Results showed that the amount adsorbed of ethyl acetate on theMIL-101was up to10.5mmol/g at288K and54mbar, while SCUT-1had a lower adsorptioncapacity for ethyl acetate. The isosteric heat of adsorption of ethyl acetate on the MIL-101and SCUT-1crystals revealed a similar trend: The isosteric adsorption heats increased slightlywith the amounts adsorbed of ethyl acetate, implying the existence of favorable lateralinteractions between ethyl acetate molecules. The diffusivity coefficients of ethyl acetatewithin MIL-101and SCUT-1crystals were all about10^-10cm²/s.