Europium(III) functionalized 3D covalent organic framework for quinones adsorption and sensing investigation

Chemical functionalization is essential for tuning the physical-chemical characters and broadening the potential applications of covalent organic frameworks (COFs). Based on the multistep postsynthetic modification strategy, Eu (III)-functionalized 3D COF (Eu-3D-COF) was prepared by grafting of Eu (III) onto the carboxyl-funtionalized 3D-COF (COOH-3D-COF). With micropores dominated microspheres structure, Eu-3D-COF exhibited superior adsorption affinity to multi-rings contained quinones based on the π-π interaction, coordination and hydrogen-bonding interactions, especially to 9,10-phenanthrenequinone (PQ) whose adjacent carbonyl oxygens resulting preferable synergistic chelation interaction with Eu(III) was responsible for the maximum adsorption capacity, which was confirmed by instrumental characterizations. The adsorptivity of Eu-3D-COF was apparently improved in comparison with COOH-3D-COF. More importantly, grafting of Eu(III) turned on the fluorescence of the COF, making Eu-3D-COF also a superior chemosensor for sensing application. Its fluorescent can be selectively quenched by quinones, especially by PQ based on the PQ-Eu and PQ-COF interactions co-dominated energy transfer. Therefore, both as an adsorbent and a chemosensor, the multi-functional COF was explored for quinones adsorption and sensing detection investigation in detail. Eu-3D-COF has promising application potentials for hazardous quinones adsorption and sensing detection, which also opens new perspectives for inorganic-organic 3D-COF construction and multi-functional applications.