Selective fluorescent sensing and photocatalytic properties of three MOFs based on naphthalene-1,4-dicarboxylic acid and 2,4,5-tri(4-pyridyl)-imidazole

Abstract

The solvothermal reactions of M^II (M = Mn, Zn, Cd) ions with naphthalene-1,4-dicarboxylic acid (H₂L) and 2,4,5-tri(4-pyridyl)-imidazole (Htpim) gave rise to three MOFs, [Mn(L)_0.5(L)_0.5(Htpim)₂]_n (1), [Zn₄(L)₄(Htpim)₂]_n (2) and [Cd₄(L)₄(Htpim)₂(DMF)₂]_n (3). Single-crystal X-ray diffraction analyses indicate that compounds 1–3 display diverse topologies. 1 possesses a 2D 4⁴ network constructed by linking Mn centers, compound 2 exhibits a 3D (3,4,6)-connected {4·6²}₂{4²·6⁴}₂{4²·6⁸·8²·10³} net interlinked by [Zn₂L₄] units, while compound 3 presents a 3D (3,7)-connected {4²·5}{4⁶·5⁵·6⁸·7²} framework assembled by dinuclear Cd nodes. 1 and 3 display high sensitivity in the detection of nitrobenzene (NB) as fluorescent sensors and Ca²⁺ or Co²⁺ ions as luminescent probes. Moreover, 3 exhibits a relatively good photocatalytic activity towards the degradation of rhodamine B (RhB) in aqueous solution under UV irradiation.