A modular approach for the synthesis of highly ordered porous and chiral auxiliary (Evans auxiliary) decorated metal-organic frameworks is developed. Our synthesis strategy, which uses known porous ...structures as model materials for incorporation of chirality via linker modification, can provide access to a wide range of porous materials suitable for enantioselective separation and catalysis. Chiral analogues of UMCM-1 have been synthesized and investigated for the enantioseparation of chiral compounds in the liquid phase and first promising results are reported.
The switching mechanism of the flexible framework Zn4O(benztb)1.5 (benztb=N,N,N’,N’‐benzidine tetrabenzoate), also known as DUT‐13, was studied by advanced powder X‐ray diffraction (PXRD) and gas ...physisorption techniques. In situ synchrotron PXRD experiments upon physisorption of nitrogen (77 K) and n‐butane (273 K) shed light on the hitherto unnoticed guest‐induced breathing in the MOF. The mechanism of contraction is based on the conformationally labile benztb ligand and accompanied by a reduction in specific pore volume from 2.03 cm3 g−1 in the open‐pore phase to 0.91 cm3 g−1 in the contracted‐pore phase. The high temperature limit for adsorption‐induced contraction of 170 K, determined by systematic temperature variation of methane adsorption isotherms, indicates that the DUT‐13 framework is softer than other mesoporous MOFs like DUT‐49 and does not support the formation of overloaded metastable states required for negative gas‐adsorption transitions.
Breathe! Combining synchrotron in situ PXRD with gas adsorption has shed light on the mechanism of guest‐induced breathing in dynamic DUT‐13 framework. In the contracted‐pore phase, the crystal has pores half the volume of those in the open‐pore phase; this is consistent with the adsorption isotherms. Methane physisorption isotherms at different temperatures indicate the softness of the framework.
A new metal–organic framework, Cu2(mpbatb)(H2O)2 (DUT-71; DUT, Dresden University of Technology) (mpbatb, 4,4′,4″,4‴-(1,3-phenylenebis(azanetriyl)tetrabenzoate)), was prepared by a solvothermal ...reaction in a mixture of DMF and EtOH. Postsynthetic modification of DUT-71 using different neutral nitrogen-containing bridging molecules in a single-crystal to single-crystal transformation fashion results in a series of porous compounds (DUT-72, DUT-73a, DUT-73b, DUT-74, DUT-90, DUT-91, and DUT-95) with apparent BET surface area up to 2700 m2 g–1. Interestingly, the Cu–Cu distances between paddle wheels during the transformation are adapted to the bridging ligands, demonstrating the flexible character of DUT-71. After solvent removal and resolvation, a drastic color change from green to dark blue and vice versa was observed. This observation was studied in detail in situ by monitoring the adsorption of ethanol in the low-concentration region by UV/vis analysis. The correlation between the ethanol adsorption uptake and the intensity of the characteristic absorption peaks in the UV/vis spectra renders the new materials promising candidates for vapochromic sensing.
A combination of topological rules and quantum chemical calculations has facilitated the development of a rational metal–organic framework (MOF) synthetic strategy using the tritopic ...benzene‐1,3,5‐tribenzoate (btb) linker and a neutral cross‐linker 4,4′‐bipyridine (bipy). A series of new compounds, namely M2(bipy)3(btb)4 (DUT‐23(M), M=Zn, Co, Cu, Ni), Cu2(bisqui)0.53(btb)4 (DUT‐24, bisqui=diethyl (R,S)‐4,4′‐biquinoline‐3,3′‐dicarboxylate), Cu2(py)1.5(H2O)0.53(btb)4 (DUT‐33, py=pyridine), and Cu2(H2O)23(btb)4 (DUT‐34), with high specific surface areas and pore volumes (up to 2.03 m3 g−1 for DUT‐23(Co)) were synthesized. For DUT‐23(Co), excess storage capacities were determined for methane (268 mg g−1 at 100 bar and 298 K), hydrogen (74 mg g−1 at 40 bar and 77 K), and n‐butane (99 mg g−1at 293 K). DUT‐34 is a non‐cross‐linked version of DUT‐23 (non‐interpenetrated pendant to MOF‐14) that possesses open metal sites and can therefore be used as a catalyst. The accessibility of the pores in DUT‐34 to potential substrate molecules was proven by liquid phase adsorption. By exchanging the N,N donor 4,4′‐bipyridine with a substituted racemic biquinoline, DUT‐24 was obtained. This opens a route to the synthesis of a chiral compound, which could be interesting for enantioselective separation.
Tailoring of MOFs! A combination of topological rules and quantum chemical calculations support the synthesis of new highly porous metal–organic framework materials. A series of compounds with pto‐like topology and properties tailored for enantioselective separation, gas storage, and catalysis have been discovered (see figure).
Sensor antenna: Functionalization of a new robust mesoporous MOF DUT‐25 (Dresden University of Technology) is realized by simple liquid‐phase adsorption of a stimuli‐responsive guest molecule. It ...leads to a new multifunctional composite Dye@MOF material with solvatochromic behavior (see figure).
A new tool (Infrasorb-12) for the screening of porosity is described, identifying high surface area materials in a very short time with high accuracy. Further, an example for the application of the ...tool in the discovery of new cobalt-based metal-organic frameworks is given.
Microporous membranes act as selective barriers and play an important role in industrial gas separation and water purification. The permeability of such membranes is inversely proportional to their ...thickness. Synthetic two‐dimensional materials (2DMs), with a thickness of one to a few atoms or monomer units are ideal candidates for developing separation membranes. Here, groundbreaking advances in the design, synthesis, processing, and application of 2DMs for gas and ion separations, as well as water desalination are presented. This report describes the syntheses, structures, and mechanical properties of 2DMs. The established methods for processing 2DMs into selective permeation membranes are also discussed and the separation mechanism and their performances addressed. Current challenges and emerging research directions, which need to be addressed for developing next‐generation separation membranes, are summarized.
2D materials with a thickness of one to a few atoms, or monomer units, minimize transport resistance and maximize permeate flux, offering membranes for ultimate separation. Recent advances in the synthesis and fabrication of 2D materials, including functional graphene oxide, 2D transition‐metal dichalcogenides, 2D polymers, 2D metal–organic frameworks, and carbon nanomembranes are discussed, holding great potential for gas and ion separation, and water desalination.
A new mesoporous MOF, Zn4O(bpdc)(btctb)(4/3) (DUT-32), containing linear ditopic (bpdc(2-); 4,4'-biphenylenedicarboxylic acid) and tritopic (btctb(3-); ...4,4',4''-benzene-1,3,5-triyltris(carbonylimino)tris-benzoate) linkers, was synthesised. The highly porous solid has a total pore volume of 3.16 cm(3) g(-1) and a specific BET surface area of 6411 m(2) g(-1), adding this compound to the top ten porous materials with the highest BET surface area.
The targeted synthesis of a desired stereomer plays a key role in life sciences, especially in the production of drugs. Up to date, this area is dominated by homogeneous chiral catalysts. ...Metal‐Organic Frameworks (MOFs), a new class of porous materials, consisting of metal‐oxo‐clusters and multifunctional ligands could offer a platform for chiral heterogeneous catalysts combining the efficiency and in particular selectivity observed for homogeneous asymmetric catalysts with the advantages of heterogeneous catalysis. This review summarizes strategies to obtain chiral Metal‐Organic Frameworks and gives an overview about reactions that have been successfully conducted using chiral MOFs as asymmetric catalysts. In addition, some examples highlighting the stereoselective adsorption properties of chiral Metal‐Organic Frameworks are given.
With increasing demand for enatiomerically pure compounds the search for appropriate catalysts or separating materials intensifies. This review gives an overview about reactions asymmetrically catalyzed by Metal‐Organic Frameworks (MOFs), a new class of porous materials. In addition some examples concerning the stereoselective separation properties of MOFs are given.
A flexible Metal-Organic Framework Zn(4)O(BenzTB)(3/2) (DUT-13) was obtained by combination of a tetratopic linker and Zn(4)O(6+) as connector. The material has a corundum topology and shows the ...highest pore volume among flexible MOFs.
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