A Metal-Organic Framework Constructed by a Viologen-Derived Ligand: Photochromism and Discernible Detection of Volatile Amines Vapors
The detection of volatile amines has attracted great attention due to their high toxicity and wide existence. Herein, we report a new example of a metal-organic framework (Co-MOF-1) for the discriminative detection of alkylamines. Co-MOF-1 was assembled by Co(II), N3ˉ and viologen-based ligand [H2L]Cl2 ([1,1′-bis(4-carboxylatobenzyl)-4,4′-bipyridinium] dichloride), shows a 3D cationic pcu framework with 1D channels containing electron-deficient viologen units, and exhibits typical electrochemical redox properties and photochromic properties, which involves the radical formation via photoinduced electron transfer from nitrate ions and carboxylate groups in the channels to viologen moieties. More importantly, Co-MOF-1 shows different color responses to different volatile amine vapors of different types and molecular sizes, which is attributed to the electron transfer from the amine to viologen. Moreover, the reason why Co-MOF-1 can detect amines distinguishably is attributed to different sizes of substituents of amine molecules and the number of the N-H bonds of the amine molecules. Furthermore, the portable test paper was successfully prepared and provided a convenient and discernible detection of volatile amines vapors by depositing Co-MOF-1 onto filter paper, which can also be used as an erasable inkless printing medium.