Study On The Synthesis Of MOF-5and Ru(Pd)/AC Doping

MOF-5is a new-type of metal-organic materials. Because of the characters of high volume utilization, tunable structure, various pore channels, and high surface area, MOF-5is regarded as one of the promising materials in gas storage. MOF-5crystals are synthesized based on the solvothermal approach with self-assembly of Zn(NO3)2-H2O and H2BDC in DMF or NMP. And the properties of MOF-5are modified by doped with Ru/AC and Pd/AC catalysts. The powder X-ray diffraction, scanning electron microscope, thermal gravimetric analysis and FT-IR, et al, are used to character.Firstly, the effects of DMF and NMP on the properties of MOF-5during its synthesized process are studied. The results show that MOF-5_NMP has non-interpenetrated structure, high crystallinity and pore volume utilization. The cubic crystals structure is more stable and orderly with smooth surface than that of MOF-5_DMF. When the MOF-5samples exposed on the air for a long time or non-soaked in CH2Cl2or non-vacuum dried, the formation of the material framework and reduce the pore volume utilization would be effected. The DMol3simulation results show that the existence of NMP may increase the stability of MOF-5framework structure, and NMP is more easily evacuated from the framework than DMF.Secondly, precious-metal catalysts such as Ru/AC and Pb/AC catalysts to modify MOF-5_NMP, and three kinds of methods (ie, mechanical grinded, carbon bridged, pre-doped) are applied respectively. According to the X-ray diffraction spectrum results, the samples treated by mechanical grinded method show characteristic peaks of sucrose in the region of20from18°to40°. However, MOF-5_Pd_m characteristic peak at20=6.8°is very weak, and the other peak9.7°(ie, R1=17.857) is relatively stronger compared with the unmodified sample, which can be explained by the decreased pore of the sample. The samples treated ty carbon bridged method have characteristic peaks of ZnO at2θ0=32、34°nd36°, and ZnO is one of the by-products due to partial decomposition of MOF-5in the carbon bridged process, in which sucrose released more heat. The crystallinity and pore volume utilization of MOF-5Pd m and MOF-5Pd b is lower than that of MOF-5Ru m and MOF-5_Ru_b. The doped samples gained less thermal stability than MOF-5_NMP with a decomposition temperature of400℃. And the pre-doped samples have an irregular cubic structure, more surface distortions and cracks.Thirdly, the results of adsorption isotherms simulation show that when the pressure is less than107kPa, the temperature is the decisive effction factor of H2equilibrium adsorption capacity in MOF-5system. When the temperature increased, the equilibrium adsorption amount decreased. On the extremely high pressure (especially higher than107kPa), the H2equilibrium adsorption amount is very close to the saturated adsorption capacity, the effect of temperature is not the decisive factor. In the same temperature, the H2equilibrium adsorption amount of Ru doped [Zn4O(BDC)3]8greater than Pd doped system, and it is a limited extent that Ru and Pd doped [Zn4O(BDC)3]8have effect on the H2equilibrium adsorption amount.