Carbon dots as an electron extractant for enhanced photocatalytic antibacterial activity of covalent organic frameworks

Abstract

The covalent organic framework@carbon dot (COF@CD) composite was successfully constructed to achieve high-flux charge transfer and efficient photocatalytic activity for antibacterial photocatalytic therapy. Utilizing the establishment of intramolecular charge transfer between donor–acceptor (D–A) semiconductors and polymers with CO–H–N hydrogen-bonding groups, the charge transfer channel constructed by using a D–A COF semiconductor and hydrophilic CDs was built. This is the first report on hydrogen-bonded two-dimensional COF-zero-dimensional CDs for artificial antibacterial photosynthesis. In such a photocatalytic system, transient photovoltage (TPV) measurements demonstrated that CDs uniformly distributed on the surface of COF nanosheets play an important role in inhibiting charge recombination as both electron transfer and storage containers. Kinetic studies showed that the introduction of CDs greatly enhanced the charge separation efficiency by extracting abundant photogenerated π-electrons from the COF, resulting in the generation of more reactive oxygen species. COF@CDs (4 wt% CDs) present photocatalytic antibacterial activity with sterilization efficiency of over 95% in 1 h under visible light irradiation, with a decrease in the survival rate by 8.3 times compared to that of the COF. This result is attributed to the combined effect of the photoexcitation rate, carrier separation rate, and reduction rate of electrons accumulated in the CDs.