Constructure And Electrochemical Performance Of New Porous Organic Polymers

Porous organic polymers?POPs?are a class of new porous materials with periodic skeletons and highly ordered pores structures.POPs offer a unique materials platform for diverse structural and functional designs,and apply in gas storage,catalysis,photoelectric conversion and energy storage.However,the weak electrical conductivity and redox activity of POPs make their advantages far from being fully reflected in supercapacitor electrode materials.Therefore,it is important practical significance to construct new POPs electrode materials.In this project,to develop new POPs supercapacitors electrode materials,conductive units,intramolecular hydrogen bonds,nickel???coordination and donor-acceptor moieties were introduced into skeleton of polymers,and synthesize a series of functional POPs to achieve largely boosted electrochemical performance.This project is divided into four parts,and the main contents are as follows:1.The constructure of 3D thiophene-based conductive POPs and their electrochemical performance:Two 3D conductive POPs POP-1 and POP-2 were constructed by the Schiff-base reaction of tetra?4-aminophenyl?methane and 2-thenaldehyde?or2,2-bithiophene-5-carboxaldehyde?and their subsequent oxidative polymerization.X-ray single crystal diffractometer confirmed their model compound structure.FT-IR and ¹³C-NMR spectrum obviously revealed the formation of POP-1 and POP-2.SEM and TEM images of POP-1 and POP-2 showed homogenous and cross-linked network structure.N₂adsorption-desorption measurements exhibited that POP-1 and POP-2 both offered a high BET surface area with 342 and 260 m² g^-1,respectively.The electrical conductivity measurement showed that POP-1 and POP-2 powder was 2.1×10^-3 and 6.7×10^-3 S cm^-1,respectively.At the current density of 1 A g^-1,POP-2 delivered a higher specific capacitance of 332 F g^-1 and better cycle stability?capacity retention of 94%after 10000 cycles?.By two-electrode system,POP-2 offered a specific capacitance of 107 F g^-1 and an energy density of 38 Wh kg^-1.The excellent electrochemical performance should be ascribed to the following reasons:?i?3D interconnected channels offer a large specific surface area and proper pore size distribution,which is beneficial to charge transfer and the diffusion of ions.???The thiophene units were introduced into conjugated skeleton,which increased the electrical conductivity and decreased resistance of the ionic diffusion.The study offers a new strategy for constructing conductive POPs electrode materials.2.The constructure of benzobisthiazole-based 2D COF and its electrochemical performance:A benzobisthiazole-linked 2D COF?PG-BBT?was constructed via1,3,5-triformylphloroglucinol and 2,5-diamino-1,4-benzenedithiol dihydrochloride.The single crystal structure of model compound confirmed the formation of benzobisthiazole and presence of intramolecular hydrogen bonds.FT-IR,¹³C-NMR and XPS spectrum clearly demonstrated the formation of 2D PG-BBT.SEM and TEM images of PG-BBT showed flower-like morphology,which were composed of a large number of ultrathin.The EDS mapping of PG-BBT exhibited the even distribution of C,N,O and S elements.N₂adsorption-desorption measurements offered a high BET surface area of 507 m² g^-1.At the current density of 1 A g^-1,PG-BBT obtained a higher specific capacitance of 724 F g^-1 and better cycle stability?capacity retention of 96%after 10000 cycles?.By two-electrode system,PG-BBT possessed a specific capacitance of 220 F g^-1 and the highest energy density of 69Wh kg^-1.PG-BBT is much superior to BZ-BBT without hydroxyl and partially hydroxyl-functionalized PG_xBZ_1-xBBT.The results reveal that the electrochemical performance can be easily tuned by changing the number of hydroxyl groups.The excellent electrochemical performance should be ascribed to the following reasons:?i?The efficient electron transfer caused by intramolecular hydrogen bonds can increase electrochemical performance.???The redox-active benzobisthiazole unit can increase electrochemical reaction kinetics,resulting in pseudocapacitive effects.??i?The ordered porous planar structure can accelerate the mass transfer rate of ions.The design concept of enhanced intramolecular hydrogen bonds,ordered pore and redox activity sheds light on constructing advanced COF electrode materials.3.The constructure of 2D semiconducting COF with nickel???coordination and its electrochemical performance:A 2D conductive COF?Ni-COF?with square-planar Ni???coordinationgeometrywassynthesizedvia1,2,4,5-benzenetetraamine,2,5-dihydroxy-1,4-benzenedicarboxaldehyde and Ni?OAc?₂?4H₂O.FT-IR,¹³C-NMR and XPS spectrum obviously revealed the formation of Ni-COF.SEM and TEM images of Ni-COF exhibited a spherical flower-like morphology,which was composed of a large number of sheets.The EDS mapping demonstrated the even distribution of C,N,O and Ni elements.N₂adsorption-desorption measurements of Ni-COF offered a high BET surface area of 362 m²g^-1.The nickel???coordination increases the electrical conductivity and chemical stability.The electrical conductivity measurement showed that Ni-COF thin film is 1.2 S cm^-1.At the current density of 1 A g^-1,Ni-COF achieved a higher specific capacitance of 1257 F g^-1 and good cycle stability?capacity retention of 94%after 10000 cycles?.By two-electrode system,the specific capacitance of Ni-COF was up to 417 F g^-1 at 1 A g^-11 and the highest energy density was up to 130 Wh kg^-1.The capacity is superior to previously reported COFs electrode materials,which should be ascribed to the following reasons:?i?The introduction of Ni greatly increases the electrical conductivity and promotes the hydroquinone to benzoquinone transformation.???Highly conjugated 2D planar structure is beneficial to the charge transport.The design strategy of introduced Ni into COF opens a new way to built functional COF electrode materials for supercapacitors.4.The constructure of donor-acceptor 2D COF and its electrochemical performance:A donor-acceptor?D-A?COF?TTF-DAQ?was constructed by electron donor tetraformyl-tetrathiafulvalene?TTF?and electron acceptor 2,6-diaminoanthraquinone?DAQ?building blocks.FT-IR and ¹³C-NMR and XPS spectrum unambiguously demonstrated the formation of TTF-DAQ.SEM images of TTF-DAQ showed blooming flower-like structure,which was composed of numerous tightly stacked sheets.TEM images revealed the tightly stacking lead to layer-by-layer re-stacking,and can observe porous structure.The EDS mapping images of TTF-DAQ further verified the structure and the even distribution of C,N,O and S elements.N₂ adsorption-desorption measurements of TTF-DAQ offered a high BET surface area of 729 m² g^-1.At the current density of 1 A g^-1,TTF-DAQ offered a higher specific capacitance of 752 F g^-1 and excellent rate capability(remains 63%of the initial value at 10 A g^-1).By two-electrode system,TTF-DAQ showed a specific capacitance of 183F g^-1 at 1 A g^-11 and an energy density of 57 Wh kg^-1.The excellent electrochemical performance should be ascribed to the following reasons:?i?D-A building block ehhances charge transfer.???The redox activity and semiconducting nature of TTF results in fast reaction kinetics.??i?2D planar structure and high surface area can offer fast pathways for charge transfer.The strategy of introduced D-A building block into COF expands the application scope of functional COF.