Multifunctional amino-decorated metal–organic frameworks: nonlinear-optic, ferroelectric, fluorescence sensing and photocatalytic properties

Abstract

Solvothermal reactions of 2-amino-1,4-benzene dicarboxylic acid (NH2bdcH2) and N-auxiliary ligands in the presence of manganese(II), zinc(II) and cobalt(II) salts have given rise to four new metal–organic frameworks, namely, [Mn5(NH2bdc)5(bimb)5·(H2O)0.5]n (bimb = 4,4′-bis(1-imidazolyl)biphenyl) (1), [Zn(NH2bdc)(bix)·(DMF)2]n (bix = 1,4-bis(imidazol-1-ylmethyl)benzene) (2), [Co(NH2bdc)(bix)·(DMF)·(CH3CH2OH)]n (3) and [Co(NH2bdc)(bpp)]n (4) (bpp = 1,3-bis(4-pyridyl)propane). Single-crystal X-ray diffraction analyses revealed that MOF 1 displays 5-fold interpenetrating 4-connected dia 3D net; MOFs 2 and 3 are isomorphic, which possess 3-fold interpenetrating dia 3D nets; MOF 4 exhibits 4-connected sql 2D net. Noncentrosymmetric structures and multifunctionality in 1–3 are established by varying ligands and metal centers. In the solid state, polar MOFs 1–3 exhibit nonlinear-optic (NLO) and MOF 1 demonstrates typical ferroelectric behaviour with a remnant electric polarization (Pr) of 1.2 μC cm−2 and an electric coercive field (Ec) of 0.35 kV cm−1. In addition, MOF 2 could be a potential luminescent probe for detecting nitrobenzene or 2-nitrotoluene via fluorescence enhancement and has been evaluated as a promising visible-light-driven photocatalyst for degradation of organic pollutants.