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Organic amines are ubiquitous and essential in the dye, polymer, and pharmaceutical industries, but can also be highly corrosive and toxic. Developing a quick and efficient method to detect organic amines is an important challenge. In this paper, we demonstrate the detection of organic amines by colorimetric and luminescence sensing of an electron-deficient viologen metal organic material. The material, comprising 1-(3,5-dicarboxyphenyl)-4,4′-bipyridinium and Cd(II), possesses a two-dimensional framework with viologen-lined chromophores and accessible electron-deficient viologen moieties constituting Lewis acidic sites. It exhibits reversible photochromic behavior under UV–Vis light irradiation and a visual color change and fluorescence quenching upon contact with amine vapors and solutions. Due to the defined pore size of the framework, the fluorescence sensing efficiency showed organic amine size dependence. The vapochromism and fluorescence quenching is attributable to electron transfer from the organic amine to the electron-deficient viologen moiety, generating colored viologen radicals. An electron-deficient metal-organic material has successfully synthesized based on the viologen ligand, which exhibit reversible photochromic behavior and selective colorimetric and luminescence sensing of organic amines. [Display omitted] • An electron-deficient viologen metal-organic material was prepared. • Compound 1 exhibit reversible photochromic behavior under UV–visible light irradiation. • Complex 1 shows colorimetric and luminescence sensing of organic amines. [ABSTRACT FROM AUTHOR]

A feasible method to construction multifunctional hybrid compounds is the incorporation of appropriate functional inorganic and organic components through self-assembly. Naphthalene diimides (NDIs) and polyoxometalates (POMs) are two versatile building blocks that have been used in many fields. In this paper, self-assembly of electron-deficient NDI ligand and POM resulted in an organic-inorganic hybrid compound, [Ce 2 (BINDI)(DMF) 8 ]·[Mo 6 O 19 ] (1), (H 4 BINDI = N , N ′-bis(5-isophthalic acid)-1,4,5,8-naphthalene diimide), with segregated Mo 6 O 19 2− polyanions and two-dimensional cationic coordination network. Because of the photochemical activities of organic and inorganic components, this hybrid compound exhibits interesting reversible photochromic behavior under ultraviolet–visible light irradiation. XRD, EPR, and XPS studies demonstrated that the photochromic behavior resulting from the coaction of NDI and Mo 6 O 19 2− polyanions. Moreover, this hybrid material shows excellent photocatalytic degradation activity toward the methylene blue (MB) dye under visible light irradiation. [Display omitted] • A polyoxometalate/naphthalenediimide hybrid structure is prepared. • Compound 1 shows fast-responsive reversible photochromism. • Photoinduced electron-transfer generate Mo5+ and NDI radicals. • Compound 1 exhibits excellent photocatalytic activity for degradation of methylene blue. [ABSTRACT FROM AUTHOR]

The encapsulation of photoactive guests into a metal-organic framework is advantageous in endowing extra functionalities such as photochromism and photoswitchable luminescence. In this paper, a host-guest MOF material, [Zn 3 (IPA) 4 ​MV] (1) (H 2 IPA ​= ​isophthalic acid, MV·2NO 3 ​= ​1,1'-dimethyl-(4,4'-bipyridine)-1,1'-diium dinitrate) has been constructed by encapsulating simplest methyl viologen guest into the anionic MOF framework. This material exhibits reversible naked-eye detectable photochromic properties varying from colorless to blue upon UV–Vis light irradiation. The MV2+ and the short O⋯N distance between the oxygen atom and pyridine ring of MV2+ play a crucial role in the photochromism of this compound. This host-guest MOF compound shows photoswitchable luminescent properties in the solid state. More interestingly, this host-guest MOF material can be deposited on filter paper and can be employed as inkless print material by controlling the UV–Vis light irradiation with the stencil. A novel MOF-based host-guest compound was prepared by incorporating the photoactive methyl viologen into the anionic framework, which exhibit photochromism upon UV–Vis light irradiation and photocontrolled luminescence. Moreover, this compound can be used as inkless and erasable print media. [Display omitted] • A host-guest compound was prepared by incorporating the viologen into the anionic MOFs. • Compound 1 exhibits fast-responsive photochromism and reversible luminescence switching upon UV–Vis light irradiation. • Compound ​ 1 ​can be employed as inkless and erasable print media by controlling the UV-Vis light irradiation. [ABSTRACT FROM AUTHOR]