Two multifunctional luminescent cobalt metal-organic frameworks for selectively and sensitively sensing of Cu2+, MnO4- and picric acid in water

Abstract

Developing novel metal-organic frameworks (MOFs) and exploring their luminescent applications gains continuous concern. Herein, based on tetraphenylpyrazine fluorophore, two cobalt metal-organic frameworks (MOFs), denoted as {Co(HCOO)(Tipp)·H2O}n(1) and {Co(Tipp)0.5A}n(2) (Tipp ​= ​2, 3, 5, 6-tetrakis[4-[(1H-imidazole-1-yl)-methyl]phenyl]pyrazine, H2A ​= ​4, 4'-oxybisbenzoic acid), have been prepared under hydrothermal condition. Structural analysis indicates that 1 has a (4, 6)-connected 3D seh network with the point symbol of {3∙42∙52∙6}{32∙42∙52∙64∙74∙8}. 2 shows a (2, 4)-connected 2D framework with a new Schläfli symbol of {42∙82∙102}{42∙83∙10}2{4}2. Significantly, 1 and 2 can be employed as multifunctional sensors for selective and sensitive detection of Cu2+, MnO4- and picric acid in aqueous solution by fluorescence quenching. The limits of detection (LODs) for Cu2+, MnO4- and picric acid were down to 10-7 ​M and quenching constant (Ksv) values reach the level of 105 ​M-1. Moreover, the two sensors show good recyclability and can respond to analytes in a wide pH range.