| Metal-organic frameworks?MOFs?as a class of porous crystalline materials have received considerable attention in recent years due to its large specific surface area,rich porosity,tunable pore structure and easy functionalization.At present,the solvothermal method is a widely-used method for the synthesis of MOFs.However,generally this method requires the addition of a large amount of solvent that suffered from time-consuming,low autoclave availability and environmental pollution.Therefore,developing a facile and green method to prepare MOFs is an important research subject.In this dissertation,solvent-free synthesis of two important MOFs MIL-100?Cr?and MIL-53?Cr?were investigated.The specific contents are as follows:Firstly,solvent-free synthesis of MIL-100?Cr?was explored using chromium nitrate as a chromium source.The influence of some synthetic parameters including ratio of Cr?NO3?3·9H2O and BTC and crystallization time on the formation of MIL-100?Cr?was studied.The optimized synthetic conditions were Cr?NO3?3·9H2O/BTC molar ratio of 1:2,crystallization time of 24 h.The optimized MIL-100?Cr?had lower BET surface area?1077 m2/g?than that?1741m2/g?by traditional method.This method is extended to the synthesis of MIL-53?Cr?and can not achieve the desired effect.Then,solvent-free synthesis of MIL-100?Cr?was explored using chloride hexahydrate as a chromium source.The influence of some synthetic parameters including ratio of CrCl3·6H2O and BTC,crystallization time and crystallization temperature on the formation of MIL-100?Cr?was studied.The optimized synthetic conditions were CrCl3·6H2O/BTC molar ratio of 2:1,crystallization time of 15 h,crystallization temperature was 220?.The optimized MIL-100?Cr?had higher BET surface area?1848 m2/g?and pore volume?1.40 cm3/g?than that?1741m2/g,1.19cm3/g?by traditional method.Those values were improved by 5.8% and 18% respectively.Further,in the oxidation reaction of benzyl alcohol,the conversion of benzyl alcohol reached 53% over MIL-100?Cr?prepared via solvent-free method,due to it exposed more active sites,attributed to the small partical size of MIL-100?Cr?synthesized by solvent-free method.Comparatively,under the same reaction conditions,the conversion of benzyl alcohol was 40% over MIL-100?Cr?prepared via solvothemal method.Solvent-free method was extended to the synthesis of MIL-53?Cr?.Similarly,the influence of some synthetic parameters including chromium source,molar ratio of CrCl3·6H2O and BDC,crystallization time was investigated.The optimized conditions were CrCl3·6H2O as chromium source,CrCl3·6H2O/BDC molar ratio of 1.5:1,crystallization time of 48 h.Subsequently,the optimized sample under the solvent-free conditions were compared with that synthesized by solvothermal method.The results indicated that the sample prepared by solvent-free method displayed a morphology of triangular pyramid-like shape with particle length of about 1.52 ?m.Meanwhile,this matierla gave high BET surface area?1310 m2/g?and pore volume?0.84 cm3/g?close to those of MIL-53?Cr?prepared via solvothermal method.Finally,MIL-100?Cr?and MIL-53?Cr?materials with high specific surface area have been successfully prepared by solvent-free method.Also,it can be expected that this synthesis method may be further applied to the synthesis of other MOFs materials. |
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