Two novel 3D metal–organic frameworks based on two tetrahedral ligands: syntheses, structures, photoluminescence and photocatalytic properties

Abstract

Two novel metal–organic frameworks (MOFs), namely [Co₂(L1)(L2)]·4.25H₂O (1) and [Cd₄(L1)₂(L2)₂]·4H₂O·DMF (2) (H₄L1 = tetrakis[4-(carboxyphenyl)-oxamethyl]methane acid and L2 = tetrakis(imidazol-1-ylmethyl)methane), have been hydrothermally synthesized. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD), thermogravimetric (TG) analyses, UV-vis absorption spectra, optical energy gap and emission spectra. In 1, tetrahedral L1 and L2 ligands link neighboring Co(II) atoms to generate a unique 3D self-penetrating framework with a tetranodal 4-connected (6·8⁵)₂(6³·8³)(8⁶) topology. However, in 2, Cd(II) atoms are bridged by L1 and L2 ligands to furnish a 3D framework with a highly rare (4,8)-connected (4⁶)(4⁴·6²)(4¹⁰·6¹⁴·7⁴) topology. In addition, compound 1 exhibits photocatalytic activity for dye degradation under UV light or visible-light and shows good stability toward photocatalysis.