The heterostructurally mixed-linkage covalent organic frameworks for different fluorescence responses to alkaloids

Overdose of alkaloid drugs often causes significant damage to the human body. However, the researches about detecting alkaloids are rare and thus, it is urgent to develop a facile method to detect alkaloids. Here, four COFs TbAzo, HTbAzo, DHTbAzo and TpAzo with different ratios of beta-ketoenamine/imine are synthesized When the ratio of beta-ketoenamine/imine is 1/2, HTbAzo shows unique photoluminescence behavior, and the fluorescence emission is much higher than the other three COFs in water. HTbAzo shows different fluorescence responses to isoniazid (ratiometric) and colchicine (turn-off) with very low detection limits (12.60 mu M for isoniazid and 1.03 nM for colchicine). HTbAzo was also applied in fluorescence sensing of isoniazid and colchicine in human serum, and the detection limits of isoniazid and colchicine were calculated to be 71.5 mu M and 4.64 mu M in the low concentration range, respectively. In addition, HTbAzo was also used to monitor pH (turn-on) in water with excellent linear relationship in the range of pH= 4.00-12.00 and a very low detection limit of 0.02. This work provides a new idea for improving the luminescence performance of COFs, and the different fluorescence responses of HTbAzo to alkaloids and pH make it a multifunctional sensor applied in real life.

Automated summary

Overdose of alkaloid drugs can cause significant damage to the human body. However, research on detecting alkaloids is limited, so there is an urgent need to develop a simple method for detecting alkaloids. In this study, four COFs (TbAzo, HTbAzo, DHTbAzo, and TpAzo) were synthesized with different ratios of beta-ketoenamine/imine. HTbAzo showed unique photoluminescence behavior and had higher fluorescence emission than the other COFs in water. HTbAzo demonstrated different fluorescence responses to isoniazid (ratiometric) and colchicine (turn-off) with very low detection limits. It was also able to detect isoniazid and colchicine in human serum and monitor pH in water. This work provides a new idea for enhancing the luminescence performance of COFs and demonstrates the multifunctional application of HTbAzo in real life.