Multi-functional metal–organic frameworks based on H4mdip: Crystal structure, photoluminescence, selective ion-exchange and catalysis

Abstract

Four new metal organic frameworks based on flexible V-type tetracaboxylate ligands [Me₂NH][In(mdip)]·2.5DMF·4H₂O (1), [Zn₂(mdip)(bpe)₂]·3H₂O (2), [Co₂(mdip)(4,4′-bipy)₂]·2.5DMF·7H₂O (3), [Co₄(mdip)₂(μ₂-O)₂(py)₇]·3DMF·7.5H₂O (4) (H₄mdip = 5,5′-methylenediisophthalic acid, 4,4′-bipy = 4,4′-bipyridine, bpe = (E)-1,2-di(pyridin-4-yl)ethene, py = pyridine), have been synthesized by using solvothermal reactions. Compound 1 was a 3D anionic framework with a (4²·6³·8) Schläfli symbol and exhibits selective ion exchange (M = Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Cu²⁺, Fe³⁺). What is more, Compound 1 has a suitable Lewis acidity and good chemical stability, which makes it a good heterogeneous catalyst for the Friedel–Crafts alkylation of pyrrole with nitroolefins. Compound 2 has a 3D framework with a novel (6²·8⁴)(6⁴·8²)² Schläfli symbol, which is first found for 4-connected binodal network. Compound 3 exhibits a 3D open porous framework and exhibits a (4,6)-connected binodal network with a (4⁴·6¹⁰·8)(4⁴·6²) Schläfli symbol. Compound 4 crystallizes in a chiral space groupP3₂ and has a 3D 4-connected uninodal network with a Schläfli symbol of (6⁵·8). It possesses regular triangular (1D) homochiral channels with an edge of 14.7 Å along the c axis. The crystal structures and coordination modes of H₄midp, as well as regulatory effect of N-donor co-ligands in these compounds are discussed. Solid-state properties for these crystalline materials, such as thermal stability, powder X-ray diffraction have been investigated. Emissive wavelengths and the radiative lifetime of their luminescent emissions for compounds 1 and 2 have also been investigated.