Residual antibiotics in the environment and the transmission of drug-resistant genes cause harm to human health.Among many kinds of antibiotics, β-lactam antibiotics, including penicillin, amoxicillin, cefazepiline, etc., account for about 70%.
Recently, Ma Wanhong, a researcher at the Key Laboratory of the Institute of Chemistry of the Chinese Academy of Sciences (hereinafter referred to as the Institute of Chemistry), and collaborators from Beijing University of Commerce and Industry have discovered a new photocatalytic system.The research results are published in the Proceedings of the National Academy of Sciences.
At present, the treatment efficiency of commonly used biodegradable methods is reduced by the inherent antibacterial activity of antibiotic molecules themselves.The biological activity of β-lactam antibiotics is mainly derived from β-lactam quaternary ring, and the toxicity and biochemical properties of the ring-opening products are improved.How to realize the economical and efficient open-loop degradation of β-lactam tetracycline is a problem to be solved urgently.
Advanced oxidation technology can completely oxidize and decompose antibiotic molecules, but active species such as hydroxyl radicals are generally not selective and can be intercepted by other soluble organic/inorganic substances coexisting in water.
In the newly published paper, Lewis acid composite photocatalysts were prepared using transition metal ion anchoring on covalent organic framework materials (COFs), and a new photocatalytic open-loop-decarboxylation system was developed.
As a common homogeneous Lewis acid catalyst, Cu2+, Zn2+ and other transition metal ions can catalyze the hydrolysis of amide and ester bonds, but due to low hydrolysis efficiency at room temperature, it is difficult to eliminate trace antibiotic pollutants.
In response to this problem, the team found that anchoring Cu2+ to COF materials with bipyridine groups guarantees the catalytic properties of Cu2+ Lewis acids and expands the photothermal conversion effect of COFs in visible light.Visible light irradiation for 1 minute can be heated from room temperature to more than 211 ℃ at Cu2+ site under gas/solid conditions.
The catalytic system can raise the local temperature of the catalytic site to 60℃ in the normal temperature water medium, and improve the catalytic decomposition rate of β-lactam bond.The experiment showed that almost all β-lactam antibiotics could be decomposed by light irradiation within 10 minutes, and the rate was 24 times higher than that of dark reactions.
The research team said that unlike the traditional oxidative mineralization-based degradation path, the catalytic system effectively avoids the interference of dissolved organic/organic substances in water, and the biochemical properties of decomposed products can be effectively removed.
Meanwhile, compared with the traditional homogeneous Lewis acid catalysts, the open-loop decomposition products of the system are completely decarboxylated and have lower toxicity such as teratogenization, carcinogenesis and endocrine disruption.