Pyrene-Integrated Cationic Organic Network: A Dual-Functionalized Platform for Simultaneous Chromate Detection and Sequestration

Toxic heavy metal oxoanions constitute a major class of water contaminants, posing significant risks to both human health and ecosystems. Chromate (CrO₄ ^2-) is among the representative toxic heavy metal oxoanions, originating from various industrial processes and readily permeating water sources. Consequently, the efficient detection and removal of CrO₄ ^2- from water are of great importance. In this study, a series of pyrene-integrated cationic organic networks (CONs) with fluorescent properties and positively charged frameworks was synthesized. By modulating the pyrene unit content using a multivariate strategy, the CON with optimal fluorescence properties (CON-LDU8-30%) was obtained, synthesized with a 3:7 ratio of 1,3,6,8-tetra-(1<i>H</i>-imidazol-1-yl)-pyrene (TIP) to 1,3,5-tri-(1<i>H</i>-imidazol-1-yl)-benzene (TIB). In one aspect, CON-LDU8-30% exhibited high sensitivity and selectivity in detecting CrO₄ ^2-, demonstrating selective detection of CrO₄ ^2- among 16 anions via a "turn-off" fluorescence response. In another aspect, CON-LDU8-30% functioned as an efficient CrO₄ ^2- adsorbent, with a kinetic constant and adsorption capacity of 0.466 g mg^-1 min^-1 and 150 mg g^-1, respectively. Therefore, this study successfully integrates fluorescent sensing and adsorption removal functionalities within CONs, offering a promising material for addressing toxic heavy metal contamination in water.