Carbon Materials Derived From Carbonization Or Activation Of Porous Aromatic Framework Paf-1and Their Applications In Energy And Environmental Science

Energy and environmental issues are the main issues of the twenty first century.On one hand, traditional energy could not meet the ever increasing demand of humanbeings and it needs to develop new energy. On the other hand, the emission of carbondioxide during the burning of fossil fuel cause great environmental problems such asgreenhouse effect, rise of sea level and the increase of the acid of ocean, thus it isimportant to decrease the carbon dioxide concentration of the atmosphere. Porousmaterials especially porous carbons, due to their high surface area, large pore volumeand excellent physical chemistry stability show great potential for clean energystorage and carbon capture. Besides, most carbons have high conductivity and playimportant role in supercapaciors and batteries. Metal organic frameworks derivedcarbons have attracted great attention in recent years due to their high surface area,varies structures and easy of heteroatom doping. However, for preparation of carbonsfrom metal organic frameworks, the yield is very low. In comparison porous organicframeworks has experienced rapid growth in last few years. Owing to the strongcovalent linkages in these frameworks, this kind of material features high stability andhigh surface area. The high concentrations of carbon species in these materials makethem very promising as precursors for preparation of carbons.This thesis devoted to prepare porous carbons from porous organic frameworksand investigate their applications in energy and environmental science. We investigatethe factors that affect their performance in gas sorption and supercapacitors and revealseveral important issues needed to pay special attention for design porous materials.This thesis mainly including four sections as following:In chapter II, the carbonization of porous aromatic frameworks and theirapplications for clean energy storage and carbon capture are introduced. We chooseporous aromatic frameworks PAF-1as precursors for carbons preparation. Comparedwith carbons derived from metal organic frameworks, higher yield is achieved and itis easier to control the structure of the resulting carbons. The resulting carbons showtunable surface area and pore size distribution. The gas sorption experimental at low pressure show increasing gas uptake and heat of adsorption. Besides, they also showhigh selectivity for sorption of carbon dioxide from mixed gases. We demonstratedthat compared with surface area and pore volume, pore size plays more important rolefor gas sorption at low pressure. The gases are able to interact with several pore wallsin narrow pores, and increased heat of adsorption is achieved. This is very importantfor designing gas sorption materials at low pressures and low gas concentrations.KOH activation of PAF-1was discussed in chapter III. Compared with directingcarbonization of PAF-1at inert atmosphere, the resulting porous carbons show highersurface area as well as narrow pore distribution. Besides, the porous carbons showbimodal pore size distribution located at0.6-0.8nm and1.1-1.3nm. Due to thepresent of narrow micropores, the carbons show enhanced gas sorption at lowpressure and heat of adsorption. The carbons also show high gas storage at highpressure and this is attributed to the bimodal pore size distribution of the carbons. Weconclude that for gas adsorption at low pressure, pore size plays more important roleand surface area and pore volume dominated the gas storage at high pressure. Thus itis very important to design materials according to the intended use.Microspore engineering of porous carbons on the effect of capacitance wasdiscussed using carbonized porous aromatic framework PAF-1in chapter IV. Theporous carbons obtained through different carbonization methods show different porestructures enabling us to do this. We demonstrate the geometric packing of theelectrolyte ions in the pores, commensurate match of the electrolyte ions with thepores and effect of diffusion are mains factors that control and influence thecapacitance of these carbon materials. The former two factors affect the capacitance atlow current density and the latter factor affect the capacitance at high current density.The porous carbons prepared by KOH activation show both high microporous volume,which is beneficial for charge storage, and mesoporous volume, which is devoted tofast ion diffusion in the pores; properties which are highly desirable.In chapter V, we introduce the application of porous aromatic frameworks inanother kind of energy storage device--proton exchange membrane full cells. Thecation-π interaction between porous aromatic frameworks and cations makes the cations are stable in PAFs. The change of color of PAF-in acids demonstrates thiskind of interaction. Conductivity measurement demonstrated the acid immersed PAFsare very promising proton conductive materials, surpass most materials based on thispreparation method. The high stability of PAFs is another advantage of PAFs and it isable to use them as high temperature full cell proton exchange membranes. Besidesthe cation-π interaction can be extended to other metal ions such as Fe3+，Ni2+，Co2+，Ag+. Using the catalysis property of these metals, a new kind of catalysis materialsmay be developed. This chapter opens new ways for the application of porousaromatic framework materials.In conclusion, based on the current hot topic of energy and environmental issues,by using of porous aromatic framework as starting materials, a series of energystorage materials were developed and the factors that affect their performance werediscussed. This thesis provides new directions for designing materials that used inenergy and environmental science.