Synthesis And Applications Of Hierarchical Porous Polymers With Hypercrosslinked Benzo-heterocyclic Frameworks

Porous polymers are widely used in gas storage and separation,contaminant removal,catalysis and drug delivery,due to their large surface area,low skeletal density,high physicochemical stability and synthetic diversity.Based on the molecular composition,porous polymers can be classified as covalent organic framework(COFs),hypercrosslinked polymer(HCPs),conjugated microporous polymer(CMPs),and inherently microporous polymer(PIMs).Among these porous polymers,hypercrosslinked polymers(HCPs)are a kind of microporous amorphous polymers with a low density,high specific surface area,which have potential applications in gas adsorption and separation,heterogeneous catalysis,drug delivery and chromatographic separation.Hierarchical porous polymers with more than one pore size distributions can effectively anchor noble metal nanoparticles and circumvent the limitation of the reactants diffusion.In this thesis,a simple and straightforward strategy is reported to knit benzoheterocycles to synthesize a series of hierarchical porous polymers with a high surface area and abundant N sites.Substituents on the benzene rings can efficiently limit over polymerization,and lead to the formation of substantial cleavage and large pores in the frameworks.As-synthesized hierarchical polymers can be directly used to stabilize Pd nanoparticles to obtain Pd/Polymer catalysts,which show persistent high activity and high selectivity in the solvent-free oxidation of benzyl alcohol.Meanwhile,iron is an excellent catalyst for carbon graphitization.The abundant nitrogen sites in the polymer to immobilize the ferric chloride catalyst.After carbonization at high temperature under nitrogen atmosphere,graphitized hierarchical porous carbons can be obtained,which possesses high ORR catalytic activity and stability in electrochemical catalysis.The main achievements are as following:1.We report a simple and straightforward route to knit a series of benzoheterocycles(indane,indoline,indole and tetrahydronaphthalene)to synthesize new hierarchical porous organic polymers with special morphological features and functional groups.Experiments show that saturated substituents on the benzene ring can efficiently limit over polymerization,and lead to the formation of more substantial cleavage and larger pores in the structure.The N doped polymer PIN-2 show outstanding ability in stabilizing ultra-small noble metal nanoparticles with uniform particle size.Pd nanoparticles stabilized by PIN-2 show excellent catalysis activity in solvent-free aerobic oxidation of benzyl alcohol with high turnover frequencies(TOFs)and high selectivity,which shows great potential applications in heterogeneous catalysis for petroleum refining and fine chemical production.2.The abundant nitrogen sites in the hierarchical porous polymer PIN-2 have a good fixation effect on iron ions.By retaining the catalyst during Friedel-Crafts reaction,we use ferric chloride as a catalyst for carbon graphitization during the pyrolysis process of PIN-2 to synthesize highly graphitized hierarchical porous carbon(MC-900).The nitrogen in the polymer can be converted into pyridine nitrogen during the pyrolysis process,which can serve as active sites for the oxygen-catalyzed oxygen reduction reaction(ORR).The graphitized nitrogen-doped hierarchical porous carbon catalyst MC-900 exhibits comparable ORR catalytic activity and stability compared to those of commercial Pt/C catalyst.