Donor-Acceptor Covalent Organic Polymers as Real-Time Luminescent Sensors for Detection and Removal of Nitro-Aromatics from an Aqueous Solution

Abstract

Creating suitable monitoring probes that exhibit strong fluorescence properties for sensitive detection and effective removal of nitro-aromatics remains a challenge. Herein, triazine-based N-rich donor-acceptor covalent organic polymers (TBN-COPs) with unique electron-rich channels, tunable pore size distribution, and outstanding specific surface areas were rational designed and synthesized to the highly selective detection and effective removal of nitro-aromatics. The sensing properties for electron-deficient benzene derivatives were explored. Compared with other types of TBN-COP candidates, TBN-1 showed a better luminescence response to nitro-aromatics, especially for picric acid (PA). The 0.15 ppm detection limits and 2.89*105 as Ksv could be realized for PA detection by TBN-1. Besides, there were no additional fluorescence responses to the electron rich benzene derivatives, demonstrating the specific selectivity of nitro-aromatics by TBN-1. The energy and charge transfer mechanisms for the hyper nitro-aromatics sensing properties of TBN-1 were further elucidated according to the energy level simulation, and to both the spectroscopic and electrochemical analysis. The merits of TBN-1 are unreservedly manifested when further testing the adsorption performance of TBN-1 for nitro-aromatics removal. The mechanism for the excellent nitro-aromatics adsorption performance of TBN-1 is revealed by coupling model fitting and chemical computation, which indicates the π-π stacking interaction and high electron density of the material to facilitate its combination with nitro-aromatics. Therefore, TBN-1 is a promising candidate to selectively detect and effectively remove nitro-aromatics, and can hence be applied in security checking and environmental conservation.

Keywords: Luminescent probe, Covalent organic polymers, Nitro-aromatics, Donor-acceptor structure