Covalent organic frameworks constructed step by step using a [(C3 + C2) + C2] strategy toward fluorescence detection of Fe3+

A series of new covalent organic frameworks (COFs) has been constructed step-by-step using a [(C3 + C2) + C2] strategy for the first time, all of which show selective fluorescence detection properties toward Fe3+ ions with the lowest limit of detection (LOD) down to 9.6 × 10-8 M. The fluorescence quenching is mainly attributed to the absorption competition quenching (ACQ) mechanism.