| Emerging as a new class of porous crystalline materials, MOFs, constructed byalternatively connecting metal ions with organic struts, have become a rapidlydeveloping research area and have attracted many attentions in the last years.Compared with conventional porous materials, the most intriguing merit of thismaterial is the designable frameworks with modular assembly process, which canincorporate various functions through carefully choosing the organic struts and metalspecies. One of the most intriguing features is their high porosity as well as largesurface areas, which make them good candidates in gas storage and separation,catalysis, proton conduction, sensing or recognition and so on. On the other hand, themetals or organic ligands in MOFs can be used to prepare metal/metal oxides orporous carbons and this is recently hot topic. The emergency of metal organicframework template carbon quickly attracts researchers’ attentions due to thefollowing reasons. First due to the diversity of MOFs, it is able to prepare porouscarbons with different morphology by choosing proper precursor. Second, extracarbon sources or heteroatom can be introduced to the porous MOFs to improve theproperty of the carbons. Besides, the metals in MOFs can be used to synthesizeporous carbons incorporated with metal or metal oxides and in air conditions puremetal or metal oxides can be achieved. Due to the purity and uniformity of MOFs, theprepared metal/metal oxides and porous carbons have very uniform structure andcomposite.This thesis devoted to prepare metal oxides and porous carbons from metalorganic framework and investigate their application in energy and environmentalscience. This thesis includes the following parts:In chapter II the preparation of ZnCo2O4nanoparticles was introduced byusing metal organic framework as precursor. A new3D mixed-metal organicframework (named as JUC-155) was designed and synthesized successfully. JUC-155was constructed with trinuclear metal cluster (ZnCo2) and BTC ligands. JUC-155could be easily transferred to pure phase mixed metal oxide (ZnCo2O4) nanoparticlesby thermal annealing, which promised higher conductivity and richer redox caused bycoupling of two metal species. The optimal sample at400oC exhibits higher specifcsurface area, high specific capacitance and excellent stability in aqueous alkaline electrolytes, which can be applied as an electrode material for supercapacitors. As faras we know, this is the first example using MOFs to synthesis ZnCo2O4material forsupercapacitors. The facial method can be readily extended to fabricating other porousmetal oxides for supercapacitors application.Preparation of mixed metal oxides from metal organic framework was extendedby using MOF-74in chapter III. A series of MOF-74structures with monometallic ordifferent ratio of divalent metals were prepared. These MOF-74could be easilytransferred to highly pure phase Co3O4, NiO and three kinds of NixCo3-xO4mixed-metal oxide nanoparticles by thermal annealing, which promised higher conductivityand richer redox caused by coupling of two metal species. We found that the mixed-metal oxides NixCo3-xO4had obvious advantages compared with the monometallicoxides when used for supercapacitor electrodes. What’s more important, for themixed-metal oxides, the molar ratio of the metals also significantly affects thecapacitance value of the materials. Especially NixCo3-xO4-1with the Ni(II)/Co(II)metal molar ratio1:1had the highest capacitance and excellent cycling stability. Thisis the first example of systematically investigation the effect of different metal speciesamounts on the electrochemical properties of the mixed-metal oxide materials. As animportant part of the ever increasing hot topic in the MOF-derived energy storagematerials, we believe that this work will get wide attention.By alternating the basicity of the solvent, two types of MOF-38with differentsize were synthesized by facile solvent thermal method. By thermal treatment at hightemperature, pure porous carbons can be obtained directly without any washing step.The porous carbons show similar morphology with the original MOFs and the metalzinc flowing out at its boiling point, leaving pure porous carbons. Nitrogen sorptionexperiments show that the surface area of the carbons increased with the temperatureincrease and the carbons obtained from big crystal exhibit higher surface area than thecarbons derived from small crystal. Besides, the carbons obtained from small crystalare mainly micropores while the carbons derived from big crystal show moremesopores. Gas sorption at low pressure show that the carbons exhibit high CO2, CH4and H2adsorption, implying their potential in clean energy storage and carbon capture.Especially the carbons obtained by calcination the small crystal at1000oC show highheat of adsorption for CO2, CH4and H2, with values of40.5kJ mol-1,44.5kJ mol-1,9.1kJ mol-1respectively and high selectively adsorption of carbon dioxide. Two novel metal-organic gel (Al-wet gel and Cr-wet gel) were synthesized byself-assembly of1,4-Di-(3’-acetylacetonato)benzene and corresponding transitionmetal salts, then Al-xerogel and Cr-xerogel were obtained by direct drying two wetgels. These materials were characterized by PXRD, SEM, TEM, FTIR, TGA, EDSand N2sorption experiments. The results indicated that the Al-xerogel and Cr-xerogelwere formed by uniformed spherical nanoparticals. The unique structures show highmicroporisity and a small amount of mesopores as well as high thermal stability.Furthermore, these materials performed gas adsorption properties．In conclusion, based on recently rapid developed metal organic frameworks, aseries of metal oxides and porous carbons were prepared by facile post treatment. Themetal oxides and porous carbons show great potential in energy storage and carboncapture. In view of the diversity structure and composing elements, this phesisprovides strategies for their post treatment and methods for metal oxides and porouscarbons preparation, having great significance in both academic research and practicalapplications. |
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