No abstract

Herein we propose a new approach for deducing the topology of metal−organic frameworks (MOFs) assembled from organic ligands of low symmetry, which we call net-clipping. It is based on the construction of nets by rational deconstruction of edge-transitive nets comprising higher-connected molecular building blocks (MBBs). We have applied netclipping to predict the topologies of MOFs containing zigzag ligands. To this end, we derived 2-connected (2-c) zigzag ligands from 4-c square-like MBBs by first splitting the 4-c nodes into two 3-c nodes and then clipping their two diagonally connecting groups. We demonstrate that, when this approach is applied to the 17 edge-transitive nets containing square-like 4-c MBBs, net-clipping leads to generation of 10 nets with diff erent underlying topologies. Moreover, we report that literature and experimental research corroborate successful implementation of our approach. As proof-of-concept, we employed net-clipping to form three new MOFs built with zigzag ligands, each of which exhibits the deduced topology.

Two new pillared zinc and cadmium-organic frameworks were synthesized by incorporating two different organic linkers, namely 2-aminoterephthalic acid as an oxygen-donor linker and N4,N4′-bisIJpyridin-4ylmethylene)-biphenyl-4,4′-diamine as a long pillaring strut. The structures of these two frameworks were analyzed using X-ray crystallography, FT-IR spectroscopy, thermogravimetric and elemental analyses. Their structural features as well as their stability were studied. These two MOFs having the same organic composition and the same network topology but different inorganic nodes differ in their chemical stability. Also, these two frameworks respond differently to nitrobenzene when they are used as fluorescent sensors. Furthermore, the catalytic behavior of one of these frameworks toward the Knoevenagel condensation reaction was investigated.

A new porous metal–organic framework (TMU-21) that is isostructural to our recently reported TMU-6 is introduced. The structure of this framework has been determined by X-ray crystallography and further characterized by Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetric analysis. Its structural features as well as its stability and porosity were studied. These two metal–organic frameworks are interesting candidates for a comparative fluorescence study. Thus, their potential abilities to sense nitrobenzene, benzene, and polycyclic aromatic hydrocarbons, namely, naphthalene, anthracene, and pyrene, were investigated. This study clearly shows an important contribution of extending the π-electron systems of pillaring linkers in the ability of metal–organic frameworks to sense aromatic compounds.

The structural diversity of metal-organic frameworks, MOFs, tailored engineering of these compounds is important for their use in catalytic processes. Among the MOFs tested as heterogeneous catalysts, there have been rare reports of size selective catalysts. In the present work, we could successfully indicate that subtle substrate selectivity can be induced in the catalytic system by designing a series of isoreticular MOFs with slight structural modifications.Four MOF catalysts possess imine and/or amine basic N-donor pillars bearing phenyl or naphtyl cores owing different hydrophobic character around the basic reaction center were prepared via simple mechano-chemical synthesis. They were characterized thoroughly using TG, IR and PXRD analysis. For the first time, aldol-type condensation reaction of malononitrile with ketonefunctionalized carbonyl substrates developed in the presence of the basic MOF organocatalysts.Moreover, it has been successfully showed that a subtle substrate selectivity can be addressed during the reaction of three slightly different α,β-unsaturated carbonyl compounds in contrast the effect of size control barriers that commonly direct heterogeneous reaction pathway.