A 2d Mesoporous Hydrazone Covalent Organic Framework for Selective Detection and Ultrafast Recovery of Au(Iii) from Electronic Waste

Developing a material that could simultaneously detect and recover gold ions is economically desirable. Herein, we constructed a two-dimensional mesoporous fluorescent covalent organic framework named TY-Hz COF by integrating 1,3,6,8-tetra(4-formylphenyl)pyrene (Ty) and terephthalic dihydrazide (Hz) units into a π-conjugated framework for simultaneous detection and recovery of Au(III). The TY-Hz COF suspension in water can rapidly (10 s) and sensitively response to Au (III) via electron transfer-induced fluorescence quenching or visual color change from bright yellow to dark green, and the limit of detection is as low as 17 nM. Moreover, TY-Hz COF can capture more than 92% Au (III) in the solution within 2 min with extremely fast kinetic speed and excellent selectivity with a maximum adsorption capacity of 1008.30 mg g -1 . It is worth mentioning that TY-Hz is the first COF that integrates the triple performance of Au (III) detection, adsorption and chemical reduction. Mechanistic studies reveal that the detection and adsorption behaviors are caused by the combined effect of redox, coordination effects between neutral amide functional groups and Au(III), and hydrogen bonding between protonated amides and chloroauric acid. These results suggest that TY-Hz COF possesses significant application value for gold detection and recovery in electronic waste.