Incorporating Triphenylamine Chromophores into Covalent Triazine Frameworks for Effective Photocatalytic Aerobic Oxidations
Rational design and construction of effective photocatalysts is a promising way for green and sustainable chemistry, but still a great challenge. Herein, taking triphenylamine-containing aldehydes as reactants, two covalent triazine frameworks (CTFs), tris(4-formylphenyl)amine (TPA)-CTF and tris(4-formylbiphenyl)amine (TBPA)-CTF, were rationally constructed. The strong electron donor property of the triphenylamine moieties derived from the initial reactants and the strong electron acceptor nature of the in-situ formed built-in triazine rings in CTFs endowed these robust triphenylamine-based CTFs with donor-acceptor (D-A) or donor-π-acceptor (D-π-A) structure features. Photocatalytic experiments revealed that, compared with the controlled phenyl analogue CTF, 1,3,5-tri(p-formylphenyl)benzene (TFPB)-CTF, both of the triphenylamine-based CTFs exhibited superior photocatalytic activity not only in photocatalytic hydrogen peroxide generation, but also in photocatalytic aerobic oxidations of diverse organic substrates. Theoretical studies further confirmed that their enhanced photocatalytic performance should be attributed to their unique D-A or D-π-A features in the constructed triphenylamine-based CTFs. This work successfully demonstrated that rational selection of reactants containing electron donor moieties to construct CTFs should be a reliable way for the construction of effective photocatalysts for photocatalytic oxidation reactions.