Teilweise Cer-setzt: Die partielle Oxidation inaktiver MnO-Nanopartikel mit CeIV führt zu einem effektiven MnOx-Katalysator für die photo- und elektrochemische Wasseroxidation. Im aktiven MnOx liegen gemischtvalente MnII-, MnIII- und MnIV-Spezies (grün und violett im Bild) mit Oxidobrücken (rot) sowie Defekten und Fehlstellen vor. MnOx ist analog zu Calcium-Manganoxid-Systemen, wobei die Ca-Positionen hier von MnII- oder MnIII-Ionen (grün) besetzt werden.
There is an ongoing need for explosive detection strategies to uncover threats to human security including illegal transport and terrorist activities. The widespread military use of the explosive trinitrotoluene (TNT) for landmines poses another particular threat to human health in the form of contamination of the surrounding environment and groundwater. The detection of explosives, particularly at low picogram levels, by using a molecular sensor is seen as an important challenge. Herein, we report on the use of a fluorescent metal–organic framework hydrogel that exhibits a higher detection capability for TNT in the gel state compared with that in the solution state. A portable sensor prepared from filter paper coated by the hydrogel was able to detect TNT at the picogram level with a detection limit of 1.82 ppt (parts per trillon). Our results present a simple and new means to provide selective detection of TNT on a surface or in aqueous solution, as afforded by the unique molecular packing through the metal–organic framework structure in the gel formation and the associated photophysical properties. Furthermore, the rheological properties of the MOF-based gel were similar to those of a typical hydrogel.
Sense and sensitivity on paper: A fluorescent metal–organic framework hydrogel exhibits greater detection capability for TNT in the gel state compared with that in the solution state. A portable sensor prepared from filter paper coated by the hydrogel was able to detect TNT at the picogram level with a detection limit of 1.82 ppt (parts per trillon; see figure).
Solare Brennstoffe: Verschiedene n- und p-Halbleiter wurden für die Herstellung nachhaltiger solarer Brennstoffe getestet. p-Halbleiter wie NiO, Fe3O4, Co3O4 und CuO können Kohlenmonoxid mit Wasser oder Wasserstoff zu Methan reduzieren (siehe Bild). Die höchste Methanausbeute lag bei 17.26 mmol Methan pro Katalysatorgramm und wurde mit einem NiO-Katalysator und überschüssigem Wasserstoff erhalten.
Metal–organic framework (MOF) NH2-Uio-66(Zr) exhibits photocatalytic activity for CO2 reduction in the presence of triethanolamine as sacrificial agent under visible-light irradiation. Photoinduced electron transfer from the excited 2-aminoterephthalate (ATA) to Zr oxo clusters in NH2-Uio-66(Zr) was for the first time revealed by photoluminescence studies. Generation of ZrIII and its involvement in photocatalytic CO2 reduction was confirmed by ESR analysis. Moreover, NH2-Uio-66(Zr) with mixed ATA and 2,5-diaminoterephthalate (DTA) ligands was prepared and shown to exhibit higher performance for photocatalytic CO2 reduction due to its enhanced light adsorption and increased adsorption of CO2. This study provides a better understanding of photocatalytic CO2 reduction over MOF-based photocatalysts and also demonstrates the great potential of using MOFs as highly stable, molecularly tunable, and recyclable photocatalysts in CO2 reduction.
Higher CO2 photoreduction activity than previously studied metal–organic framework (MOF) NH2-MIL-125(Ti) in the presence of triethanolamine (TEOA) as the sacrificial agent under visible light is exhibited by the amino-functionalized MOF NH2-Uio-66(Zr). The photoinduced electron transfer from 2-aminoterephthalate linkers to Zr oxo clusters was revealed for the first time by photoluminescence studies, and the generated ZrIII was detected by ESR analysis (see figure).
Metall-organische Gerüste: Eine Solvothermalsynthese mit Zn2+-Ionen und Bis(pyrazolyl)naphthalin lieferte stark haftende, elektroaktive, dünne Filme Metall-organischer Gerüste auf leitfähigen Glassubstraten (siehe Bild). Die elektrochemische Zyklierung der Filme und anschließende UV/Vis-Spektroskopie offenbaren auffallende mehrfarbige elektrochrome Charakteristika.
Assimilation of open metal sites (OMSs) and free functional organic sites (FOSs) with a framework strut has opened up a new route for the fabrication of novel metal–organic materials, thereby providing a unique opportunity to explore their multiple functionalities. A new metal–organic framework (MOF), {[Cu(ina)2(H2O)][Cu(ina)2(bipy)]⋅2 H2O}n (1) (ina=isonicotinate, bipy=4,4′-bipyridine), has been synthesized and characterized. Complex 1 is crystallized in the orthorhombic noncentrosymmetric space group Aba2 and consists of two different 2D coordination polymers, [Cu(ina)2(H2O)]n and [Cu(ina)2(bipy)]n, with entrapped solvent water molecules. Hydrogen-bonding interactions assemble these two different 2D coordination layers in a single-crystal structure with interdigitation of pendant 4,4′-bipy from one layer into the groove of another. Upon removal of guest molecules, 1 undergoes a structural transformation in single-crystal-to-single-crystal fashion with expansion of the effective void space. Each metal center is five-coordinated and thus can potentially behave as an OMS, and the free pyridyl groups of pendant 4,4′-bipy moieties and free ![[BOND]](http://onlinelibrarystatic.wiley.com/undisplayable_characters/00f8ff.gif)
C![[DOUBLE BOND]](http://onlinelibrarystatic.wiley.com/undisplayable_characters/00f8fe.gif)
O groups can act as free FOSs. Thus, owing to presence of both OMSs and free FOSs, the framework exhibits multifunctional properties. Owing to the presence of OMSs, the framework can act as a Lewis acid catalyst as well as a small-molecule sensor material, and in a similar way, owing to the presence of free FOSs, it performs as a Lewis base catalyst and a cation sensor material. Furthermore, owing to noncentrosymmetry with large polarity along a particular direction, it shows strong second-harmonic generation/nonlinear optical (SHG-NLO) activity.
Double duty: A strong second-harmonic generation/nonlinear optical (SHG-NLO)-active dynamic cocrystalline metal–organic framework (MOF) with both open metal sites and free pyridyl groups shows both Lewis acidic and Lewis basic catalytic activities along with small-solvent-molecule and cation sensing abilities (see figure; FOS = functional organic sites, OMS = open metal sites).
Nature Chemistry 5, 830 (2013). doi:10.1038/nchem.1730
Authors: Daniel Beaudoin, Thierry Maris & James D. Wuest
Modular construction using connectable molecular subunits is a powerful strategy for making new carbon-based materials. So far, large crystals have been produced only from subunits linked by weak interactions. Covalently bonded analogues have now been prepared by reversible self-addition polymerization of suitable monomers and structurally characterized by single-crystal X-ray diffraction.
Iron ORR: An ordered, mesoporous, Fe-porphyrin-like material was created through the nanocasting and pyrolysis of traditional Fe–N4 porphyrins. The resulting nonprecious metal electrocatalyst was used for the oxygen reduction reaction in both alkaline and acidic media.
