Designed synthesis of an sp 2 carbon-conjugated fluorescent covalent organic framework for selective detection of Fe 3 .

A new fully conjugated covalent organic framework material (COF TFPPy-ThDAN ) has been synthesized via the Knoevenagel condensation reaction using 1,3,6,8-tetra(4-formylphenyl)pyrene (TFPPy) as the chromogenic unit and 2,2'-([2,2'-bithiophene]-5,5'-diyl)diacetonitrile (ThDAN) as the linker. The COF TFPPy-ThDAN has been successfully prepared under the optimized conditions and showed excellent crystallinity and chemical stability. Especially, it was able to maintain its crystallinity even when immersed under harsh conditions such as HCl (3 M) and NaOH (3 M). Meanwhile, COF TFPPy-ThDAN exhibited good fluorescence properties, which could remain relatively stable under different pH conditions. Moreover, COF TFPPy-ThDAN was further employed for the detection of Fe 3+ with high sensitivity and selectivity with a limit of detection (LOD) of 1.26 μM. COF TFPPy-ThDAN with high stability and fluorescence is a promising material for chemical sensing.