Catalytic Conversion Of Biomass And Adsorption Removal Of Pollutant From Water By Using Al-based MOFs

Metal-organic frameworks (MOFs) are new members of porous nanomaterials with hybrid organic-inorganic supramolecular structures. They are much more attractive in catalysis and adsorption process in comparison with traditional porous materials becuse of their advantages such as high surface areas, well-defined structures, special metal centers (saturated and unsaturated metal sites), the ease of processability and structural diversityNowadays, the energy crisis and water contamination have become the most serious focuses which threat to the survival of mankind directly. As the only renewable carbon energy we know on the earth, biomass resource could not only supply energy, but also produce varieties of chemical materials through effective transformation. On the other hand, adsorption is one of the most effective methods for contaminant removal from polluted water. But many traditional adsorbents are selectively limited and their adsorption capacities are always low. In the context of this, it is definitely critical to develop new techniques with MOFs for biomass conversion and water treatment. Herein, several MOFs have been used in catalysis and adsorption processes. The main contents of the research are as following:(1) Two Al-MOFs were synthesized by using different organic ligands through solvothermal method, named MIL-53(Al) and NH2-MIL-101(Al). The obtained samples were characterized by a combination of physicochemical techniques such as powder X-ray diffraction (PXRD), N2adsorption/desorption measurement, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric differential thermal analysis (TG-DTA), ammonia temperature programmed desorption (NH3-TPD) and X-ray photoelectron spectroscopy (XPS).(2) MIL-53(Al) was used in hydrothermal catalytic degradation of carboxymethyl cellulose (CMC) to produce5-hydroxymethyl-furaldehyde (5-HMF),a high value-added chemical. The effects of amount and kind of catalyst used, temperature and reaction time on the productivity, as well as the reaction mechanism were investigated. Under optimum reaction conditions, a5-HMF molar yield of40.3%and total reducing sugar (TRS) molar yield of54.2%were chieved. The catalyst is hydrothermally stable to be reused three times without losing activity to a great extent. With the remarkable advantages such as the use of water as single solvent and MIL-53(Al) as a novel heterogeneous green catalyst, the work provides a new platform for the production of value added chemicals and liquid fuels from biomass.(3) An ami no functionalized MOF NH2-MIL-101(A1) was used as adsorbents to remove an anionic dye Congo red from aqueous solution. The effects of amount and kinds of adsorbent used, temperature, time and ionic strength on the removal efficiency were elaborately investigated. The results show that NH2-MIL-101(Al) possesses good adsorption efficiency for Congo red, which is far higher than bare MIL-101(Al) and other MOFs used. An adsorption capacity of1302.4mg·g-1was achieved. Moreover, the results from adsorption kinetic modelling, isotherm modelling and thermodynamics behavior analysis confirmed a Lagergren pseudo-second order model and intraparticle diffusion is the rate-determining step. The Langmuir model correlated well with the experimental data. Analysis of standard free energy (△G), the enthalpy (△H’) and entropy (△S’) demonstrated that the adsorption process was spontaneous and exothermic.(4) NH2-MIL-101(Al) was used as adsorbents to remove heavy metal contaminant arsenic (As) from water. The effects of amount and kinds of adsorbent used, temperature, time and ionic strength on the removal efficiency were studied. An adsorption capacity of85.2mg·g-1for arsenic was achieved. The results from adsorption kinetic modelling, isotherm modelling and thermodynamics behavior analysis confirmed a Lagergren pseudo-second order model and intraparticle diffusion is the rate-determining step. The Langmuir model correlated well with the experimental data. Analysis of standard free energy (△G’), the enthalpy (△H) and entropy (△S’) demonstrated that the adsorption process was spontaneous and exothermic.(5) NH2-MIL-101(Al) was used as adsorbents to remove phosphorus from polluted water. The effects of different adsorbents, temperature, time and ionic strength on the removal efficiency were studied. The adsorption capacity for phosphorus was42.8mg·g-1. The adsorption kinetic modelling, isotherm modelling and thermodynamics behavior analysis confirmed a Lagergren pseudo-second order model and intraparticle diffusion is the rate-determining step in the process of adsorption. The Langmuir model correlated well with the experimental data. The results of standard free energy (△G’), the enthalpy (△H’) and entropy (△S’) analysis demonstrated that the adsorption process was spontaneous and exothermic.