Study Of The Synthesis, Characterization, And Catalytic Properties Of Metal-organic Framework Materials

Metal-organic frameworks (MOFs) are a novel class of porous materials which haveimportant application value, and previous researches focused more on the design, synthesisand application of bulk MOFs materials; in recent years, nanometer-sized metal organicframeworks (NMOFs) have received great attention due to their interesting characteristics forvarious nanotechnology and device integration, however, the controllable synthesis ofmorphology and size of NMOFs still faces enormous challenges. In this paper, three types oftypical MOFs including HKUST-1, Tb(BTC)(H2O)(DMF) and Er(BTC)(DMF)(DMSO) withdifferent size and morphology were synthesized using solvothermal method; the catalyticproperties of HKUST-1crystals were investigated, and HKUST-1membranes on copper meshsupport were prepared by seeded-growth method.Firstly, three types of modulators including sodium formate, sodium acetate andtriethylamine were used to tailor the morphology and size of HKUST-1crystals. Sphericalmonodisperse submicrometer crystals with sizes in the range of80250nm were prepared byaltering the amount of sodium acetate. The size of crystals synthesized with different amountsof sodium acetate is much larger. Hierarchical octahedral crystals were obtained whentriethylamine was used as modulator, and the formation mechanism of hierarchicaloctahedral-shape crystals is a typical “two-stage growth process”. Catalytic properties ofHKUST-1crystals for the oxidation of benzyl alcohol were studied; the effects of catalyst size,reaction temperature and time were investigated. The results show that the conversion ofbenzyl alcohol and the selectivity of benzyl aldehyde reach59.12%and72.52%respectivelyunder the temperature of80oC for6hours. HKUST-1membranes were prepared byseeded-growth method, and the influence of reaction time, the concentration of mothersolution, and the number of reaction were studied. It shows that the best reation time andconcentration of mother solution are12hours, n=0.8, respectively; it is helpful to increase the number of reaction for the formation of dense membranes.A lanthanide metal-organic framework, Tb(BTC)(H2O)(DMF), with variousmorphologies was synthesized using sodium acetate, ammonia water and triethylamine asmodulators under mild conditions. Belt-like, potato-like, flower-like crystals and nanocrystalswere obtained by altering the concentration of sodium acetate; this indicates that the additionof sodium acetate can effectively reduce the crystals size. In the same condition, nanocrystalswere not obtained when ammonia water or triethylamine was used to adjust the pH values ofsolution. A lanthanide metal-organic framework, Er(BTC)(DMF)(DMSO), was not obtainedwhen sodium acetate was used as modulator, which demonstrates that there are somelimitations in choosing modulator; However, through adding a different amount oftriethylamine, Er(BTC)(DMF)(DMSO) crystals with sizes in the range of1-2μm weresynthesized.