Phase-pure NU-901 was functionalized with amines through solvent-assisted linker incorporation resulting in more than double the typical CO2adsorption capacity.

Nerve agents are among the most toxic substances known to man. Recent events in Syria, Malaysia, and the UK illustrate that the threat of these substances is real and actual. The timely detection and identification of nerve agents is of great importance to facilitate timely decontamination or medical countermeasures. In this work, an effective and sensitive detection system, based on the metal−organic framework (MOF) NU-1000, was developed for the disclosure of V-agents, a class of nerve agents that is very persistent, highly toxic, and difficult to detect. NU-1000 is a zirconium-based MOF that can hydrolyze VX into a nontoxic phosphonic acid and the thiol 2-(diisopropylamino)ethanethiol. In this work, it was hypothesized that the four noncoordinating sites that are present on each Zr-building brick of this MOF could be functionalized with the two carboxylates present in 5,5′-di-thio-bis(2-nitrobenzoic acid), DTNB. This dimeric (RS-SR) compound efficiently reacts with thiols by S−S bond exchange and results in the release of the chromophore RS-H. Thus, the target hybrid material (DTNB@ NU-1000) was expected to degrade VX and at the same time give a visual color response upon reaction of the thiol-containing degradation product of VX with MOF-bound DTNB. We here report that DTNB@NU-1000 can be readily synthesized and that it is surprisingly active in the degradation of VX in neutral buffer. Moreover, the degradation of VX resulted in a color response, the intensity of which showed linear correlation with the VX concentration used. The applicability of this material was illustrated by a proof-of-concept detection kit for VX-contaminated surfaces, as exemplified with VX-contaminated metal panels coated with military paint [chemical agent resistant coating]. This procedure requires minimal training burden, and VX contamination down to a level of about 1−2 μg/cm 2 could be reliably visually established, during a total handling time of 20 min.

Experimental photoelectron and computational results show diniobium-carbon (Nb(2)C(n)) clusters to coexist in multiple structural isomers: three-dimensional geometries, planar rings, and linear chains. Three-dimensional clusters having up to five carbons are formed preferentially with Nb-Nb bonding, whereas only Nb-C bonding is observed experimentally at six carbons. Clusters consisting of an odd number of atoms are also observed with linear geometries. The larger binary clusters (n > or = 7) display properties similar to those of pure carbon clusters. We provide evidence for niobium substitution of carbon atoms.

The influence of source conditions on vanadium-carbon cluster formation in a methane-vanadium plasma is explored and analyzed by photoelectron spectroscopy, revealing that the metal-carbon ratio has substantial influence over the cluster products. Experiments that employ large methane content produce carbon-rich mono- and divanadium carbides. The carbon-rich clusters show a preference for the formation of cyclic neutral and linear ionic structures. When the methane concentration is decreased, VmCn clusters are formed with m = 1-4 and n = 2-8. The photoelectron spectra of clusters formed under these conditions are indicative of a three-dimensional network. We have measured a significantly lower vertical electron affinity for the VC2, V2C3, and V4C6 clusters compared with proximate species. Interestingly, the VC2 species is a proposed building block of the M8C12 Met-Car cluster, and the 2,3 and 4,6 clusters correspond to the 1/4 and 1/2 Met-Car cages, respectively. This correlation is taken as evidence of their importance in the formation of the larger Met-Car species. These results are supported by density functional theory (DFT) calculations carried out at the PBE/GGA level.

Ab initio molecular dynamics (AIMD), based on density functional theory, has been used to develop and test a model for amorphous Zr­(OH)4, which is of interest as an agent for the adsorption of toxic gases. Beginning with an idealized and highly ordered structure based on two-dimensional layers of polymeric Zr­(OH)4, AIMD at 300 K and above yields an amorphous structure. Disordering is seen to occur concomitantly with a reaction between acidic bridging OH sites and basic terminal OH to produce H2O and Zr–O–Zr bridges. The modeling also shows that Zr­(OH)4 can be maintained in an artificial ordered state either by a regular array of hydrogen bonds within layers or by interaction between layers. Radial distribution functions and distributions of hydrogen-bond parameters are calculated for both the ordered and the amorphous structures, and a comparison between the two sets of results provides insight regarding the nature of the amorphous state. Infrared and proton nuclear magnetic resonance spectra are computed for the amorphous model, and chemical properties are evaluated by examining the acidity of different types of OH groups and also the reactions with SO2 and CO2. In particular, various mechanisms leading to sulfite formation during exposure to SO2 are examined in some detail. In all cases, good agreement with experiment is found, which indicates that the model is a suitable basis for analyzing the adsorption properties of amorphous Zr­(OH)4.