Donor-acceptor regulation in covalent organic frameworks promoting photocatalytic water oxidation
In order to explore the influence of electron donor-acceptor structure on the photocatalytic performance of covalent organic frameworks(COFs),C=C linked NN-COF and NT-COF were synthesized form the condensation reaction of basic building monomer N,N'-p-acetonitrile-phenyl-1,4,5,8-naphthalimide(NBA)with electron-donating tri(4-formyl)aniline(N-CHO)and electron-withdrawing 1,3,5-tri-(4-formyl)triazine(TFPT),respectively.The structure,morphology and photoelectric properties of the two COFs were characterized by XRD,FTIR,13CNMR,XPS,SEM,TEM,EDS and UV photoelectron spectroscopy(UPS),and their photocatalytic water oxidation(OER)performance were investigated.The results showed that,compared with NN-COF,NT-COF exhibited closer interlayer π-π packing,wider visible light absorption range and stronger photogenerated carrier generation ability due to their electron absorbing ability and high planarity of the triazine units.When Co(NO3)2·6H2O was added as cocatalyst,the average oxygen evolution rates of NN-COF and NT-COF were 303.73 and 449.53 μmol/(g·h).The electron-deficient naphthalimide unit of NT-COF was more conducive to the accumulation of photo-generated holes on its heteroatoms,thus demonstrating higher catalysis efficiency for the oxidation reaction of water molecules.
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