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

Abstract

By using 1,3-di(4-pyridyl)-propane (dpp) as templates or structure-directing agents (SDAs), a series of hybrid cuprous halogenides, namely, [H₂dpp]₂[Cu₄I₈]·H₂O (1), [H₂dpp][Cu₂I₄] (2), [H₂dpp]₂Cu₁₁I₁₅ (3) and [H₂dpp]₂Cu₁₁Br₁₅ (4), have been solvothermally prepared and structurally characterized. Despite the similar chemical compositions, compound 1 features a zero-dimensional (0D) [Cu₄I₈]⁴⁻ unit and compound 2 contains one-dimensional (1D) [Cu₂I₄]²⁻ chains, which are both separated by [H₂dpp]²⁺ organic cations. Compounds 3–4 contain two-dimensional (2D) microporous [Cu₁₁X₁₅]⁴⁻ (X = I, Br) layers composed of the [Cu₉X₁₇] 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.