Preparation Of Microporous Organic Polymers With Different Morphologies And Study On Their Properties

Recently,microporous organic polymers?MOPs?as a class of emerging porous materials have attracted more attention due to their porosity,high surface areas,low skeletal density,high chemical/thermal stability and easy functionalizations.In this regard,MOPs are widely applied in adsorption,catalysis,energy storage and so on.However,MOPs with the same chemical composition can exhibit different properties through simply altering their nanostructure.Therefore,many works are focused on the morphology of MOPs.The main work of this doctoral dissertation is seeking novel methods to fabricate MOPs with unique well-controlled morphology and various functionalizations,and exploring their applications in adsorption,supported metal catalysis and energy storage.Firstly,the well-defined polylactide-b-polystyrene diblock copolymers were synthesizedviaring-openingpolymerization?ROP?andreversible addition-fragmentation chain transfer?RAFT?polymerization.Then,hollow microporous organic nanospheres?H-MONs?were prepared by using PLA-b-PS as precursors based on a hyper-cross-linking mediated self-assembly strategy with AlCl₃as catalyst and tetrachloromethane?CCl₄?as solvent and cross-linker.In this process,hyper-cross-linking PS blocks formed microporous organic shell frameworks and the removed PLA blocks produced hollow mesoporous core structures.Importantly,the hyper-cross-linking mediated self-assembly strategy was proposed to explain the formation mechanism of H-MONs.Moreover,based on the hyper-crosslinking rigid microporous organic frameworks,hollow microporous carbon nanospheres?H-MCNs?could be achieved by the further pyrolysis.The obtained H-MCNs as electrode materials of supercapacitor exhibited excellent electrochemical performance with specific capacitances of up to 145 F g^-1 at 0.2 A g^-1,with almost no capacitance loss even after 5000 cycles at 10 A g^-1.Our strategy represents a new avenue for the preparation of microporous organic polymers with controlled morphology and various potential applications.Here,when CCl₄ was used as cross-linker,abundant-CO-crosslinking bridges bonds will formed after Friedel-Crafts alkylation reaction,which could be further used as active sites to skillfully introduce ethylenediamine into the hyper-cross-linking microporous skeleton shell of hollow nanospheres based on Schiff base reaction to give ethylenediamine-functionalized hollow microporous organic nanospheres?NH₂-HMONs?.Due to the unique spherical nanostructure and the interaction between nitrogen atom and iodine,NH₂-HMONs exhibited outstanding adsorption capacity and efficiency for iodine.Owing to their high surface area and strong coordination ability of the amine to the palladium nanoparticles?Pd NPs?,the NH₂-HMONs could be considered as an excellent substrate to immobilize Pd NPs to form Pd@NH₂-HMONs composite.The catalysis results indicated that Pd@NH₂-HMONs showed outstanding catalytic activity and stability in the hydrogenation of nitroarene to aniline analogues.To further expand the morphology design of MOPs,the microporous organic nanotubes?MONTs?could be constructed by using PLA-b-PS as precursors based on Scholl reaction that is a coupling reaction between two arene compounds with the aid of a Lewis acid and a protic acid through eliminating two aryl-hydrogens between adjacent phenyl rings to form a new aryl-aryl bond.In this process,the PS blocks formed the microporous organic frameworks of nanotubes through C-C coupling reaction,while the PLA segments were completely degraded to produce the hollow mesoporous tubular structures.The mechanism of nucleation-to-growth based on hyper-cross-linking mediated self-assembly strategy was provided to explain the formation of MONTs.Owing to their high special surface area and hydrophobic organic prorous framework,the obtained MONTs exhibited outstanding adsorption capacity and efficiency for p-cresol and different organic vapors.Moreover,microporous carbon nanotubes?MCNTs?could be prepared by the further carbonization.The resultant MCNTs as electrode materials of supercapacitor displayed excellent electrochemical performance.The three-arm branched microporous organic nanotube networks?TAB-MONNs?were prepared from molecule templating of three-arm branched core-shell bottlebrush copolymers and Friedel-Crafts alkylation reaction.The unique three-arm branched bottlebrush copolymers were firstly synthesized by a combination of atom transfer radical polymerization?ATRP?,RAFT and ROP techniques.The prepared bottlebrush copolymers underwent Friedel-Crafts alkylation hyper-crosslinking reaction with FeCl₃ as catalyst and FDA as extra cross-linker to give target TAB-MONNs.In this process,the outer PS blocks formed the microporous organic frameworks of nanotubes through Friedel-Crafts alkylation reaction,while the PLA segments were completely degraded to produce the hollow mesoporous tubular structure.In this approach,the length and diameter of branched tube units can be well-controlled by rational molecular design.Moreover,owing to the unique three-arm tubular nanostructure,the as-prepared TAB-MONNs exhibited a superior adsorption rate for Rhodamine 6G?R6G?and p-cresol comparing to microporous materials with irregular morphology.The other work in this PhD thesis is in-situ synthesis of dual-phase thermosensitive ultrasmall gold nanoparticles?USGNPs?with average size of 1.7 nm usingPoly?N-isopropylacrylamide?-block-Poly?N-phenylethylenediamine methacrylamide??PNIPAM-b-PNPEDMA?amphiphilic diblock copolymers as ligands and reducants.The PNPEDMA block promotes the in-situ reduction of gold precursors to zero-valent gold and subsequently binds onto the surface of gold nanoparticles,while the PNIPAM acts as a stabilizing and thermosensitive block.The as-synthesize USGNPs exhibited excellent stability for several months in aqueous solution and dry solid state.Besides,the USGNPs stabilized by thermosensitive PNIPAM layer exhibited a sharp,reversible,clear-opaque transition in aqueous solution between 30 and 38 ^oC.An unprecedented finding was that the above USGNPs also showed a reversible,soluble-precipitate transition in nonpolar organic solvent such as chloroform around 0 ^oC under acidic media.