Di-pyridyl organic cation directed hybrid cuprous halogenides: syntheses, crystal structures and photochromism and photocatalysis.

By using 1,3-di(4-pyridyl)-propane (dpp) as templates or structure-directing agents (SDAs), a series of hybrid cuprous halogenides, namely, [H2 dpp]2 [Cu4 I8 ]·H2 O (1), [H2 dpp][Cu2 I4 ] (2), [H2 dpp]2 Cu11 I15 (3) and [H2 dpp]2 Cu11 Br15 (4), have been solvothermally prepared and structurally characterized. Despite the similar chemical compositions, compound 1 features a zero-dimensional (0D) [Cu4 I8 ]4- unit and compound 2 contains one-dimensional (1D) [Cu2 I4 ]2- chains, which are both separated by [H2 dpp]2+ organic cations. Compounds 3-4 contain two-dimensional (2D) microporous [Cu11 X15 ]4- (X = I, Br) layers composed of the [Cu9 X17 ] unit interconnected by [CuX4 ] tetrahedra. The UV-vis diffuse-reflectance measurements reveal that the compounds 3-4 exhibit semiconducting behaviors with narrow band gaps of 1.48 and 2.21 eV, respectively, which lead to efficient photocatalytic degradation activities over an organic pollutant under visible light irradiation. The possible photocatalytic mechanism is also proposed based on experimental and theoretical studies. Furthermore, compound 1 shows interesting photochromism behavior maybe owing to the photo-induced intermolecular charge transfer.