Catenation

Abstract: A family of isoreticular chiral metal−organic frameworks (CMOFs) of the primitive cubic network topology was constructed from [Zn4(μ4-O)(O2CR)6] secondary building units and systematically elongated dicarboxylate struts that are derived from chiral Mn-Salen catalytic subunits. CMOFs 1−5 were synthesized by directly incorporating three different chiral Mn-Salen struts into the frameworks under solvothermal conditions, and they were characterized by a variety of methods, including single-crystal X-ray diffraction, PXRD, TGA, and 1H NMR. Although the CMOFs 1 vs 2 and CMOFs 3 vs 4 pairs were constructed from the same building blocks, they exhibit two-fold interpenetrated or non-interpenetrated structures, respectively, depending on the steric sizes of the solvents that were used to grow the MOF crystals. For CMOF-5, only a three-fold interpenetrated structure was obtained due to the extreme length of the Mn-Salen-derived dicarboxylate strut. The open channel and pore sizes of the CMOF series vary systematical...

Abstract: A strategy to control framework-catenation in MOFs has been presented; contributions to hydrogen uptake from interpenetration and unsaturated metal centers have been resolved.

Abstract: Metal−organic frameworks (MOFs), a hybrid class of materials comprising inorganic nodes and organic struts, have potential application in many areas due to their high surface areas and uniform pores and channels. One of the key challenges to be overcome in MOF synthesis is the strong propensity for catenation (growth of multiple independent networks within a given crystal), as catenation reduces cavity sizes and diminishes porosity. Here we demonstrate that rational design of organic building blocks, which act as strut-impervious scaffolds, can be exploited to generate highly desired noncatenated materials in a controlled fashion.

Abstract: Catenation, in the form of interpenetrating and interweaving,[1] has been a major concern in the design of low-density (porous) structures due to the following widely held beliefs: a) the use of long links for the design of frameworks with large pores results in catenated structures and thus small pores, b) highly catenated frameworks typically have low porosity ( 20%), and c) catenation contributes negatively to the structural stability and porosity of open frameworks.[1, 2] We recently found in the chemistry of metal-organic frameworks (MOFs) that discrete secondary building units (SBUs) are important for designing structures with attributes that disprove the universality of b) and c); specifically, maximally interpenetrating MOFs have been shown to have highly porous ( 65%) structures, and interweaving in open frameworks has been recognized and used for the design of structures with reinforced walls and permanent porosity.[1c±d, 3] Herein, we introduce the use of infinite SBUs toward addressing the point presented in a). Specifically, we show that MOF-69A, [Zn3(OH)2(bpdc)2] ¥ 4DEF ¥ 2H2O (bpdc 4,4 -biphenyldicarboxylate; DEF N,N -diethylformamide), and its 2,6-naphthalenedicarboxylate (ndc) analogue MOF-69B have three-dimensional (3D) structures constructed from infinite Zn-O-C SBUs and long bpdc or ndc links that expand the Al net in SrAl2 and provide a framework where catenation is forbidden. Infinite Zn-O-C SBUs were produced by subjecting reaction mixtures that typically giveMOF-5 to increasing amounts of H2O2. These solutions were monitored for the appearance of crystalline solids. A single-crystal X-ray diffraction study[5a] performed on a rodlike colorless crystal of MOF-69A delocalized electrons on the linkers between the chains, exhibit very low TN values (4 ± 10 K). The presence of these electrons drastically enhances the magnetic characteristics of these solids above the strategic borderline of liquid nitrogen temperature. This renders porous solids magnetic with sufficiently high and available ordering temperatures which could now find applications, for example, in magnetic sorting.