Room-temperature ultra-sensitive trimethylamine and ethylenediamine assays for fish freshness detection based on an imine-covalent organic framework

Abstract

Covalent organic frameworks (COFs) are next-generation materials with pre-designed π-electronic backbones and highly ordered topologies that hold promise for use in fast gas sensing detection. Inspired by this, we synthesised imine COFs (COF_RT) using melamine and terephthaldehyde with the aid of a catalyst (Sc(OTf)₃) at room temperature. Based on density functional theory calculations, the COF_RT material was prepared with a stronger adsorption capacity for trimethylamine and ethylenediamine. Results showed that the COF_RT sensor exhibited excellent selectivity for trimethylamine and ethylenediamine and high responses (up to 3079.2% and 1540.3%, with detection limits as low as 28 ppb and 405 ppb, respectively), and it was able to complete the response recovery cycle within 18–26 s. In addition, the sensor was successfully used for monitoring fish freshness in real environments. Compared with solvothermal methods, the detection method using the COF_RT sensor was more energy efficient and offered a wider range of applications. In addition, this study provides valuable insights into the development of amine gas sensors using imine-based COFs and paves the way for the development of room-temperature synthesis of COFs materials as chemical gas sensors.