Handedness or chirality determination is a challenging and important topic in various fields including chemistry and biology, as two enantiomers have the same composition and mirror symmetry related structures, but might show totally different activities and properties in enantioselective separations, catalysis and so on. However, current methods are unable to reveal the handedness locally of a nanocrystal at the atomic-level in real-space imaging due to the well-known fact that chiral information is lost in a two-dimensional projection. Herein, we present a method for handedness determination of chiral crystals by atomic-resolution imaging using Cs-corrected scanning transmission electron microscopy. In particular, we demonstrate that enantiomorphic structures can be distinguished through chiralitydependent features in two-dimensional projections by comparing a tilt-series of highresolution images along different zone axes. The method has been successfully applied to certify the specific enantiomorphic forms of tellurium, tantalum silicide and quartz crystals, and it has the potential to open up new possibilities for rational synthesis and characterization of chiral crystals.
Ammonia borane (AB) has been regarded as a promising
material for
chemical hydrogen storage. However, the development of efficient,
cost-effective, and stable catalysts for H2 generation
from AB hydrolysis remains a bottleneck for realizing its practical
application. Herein, a step-by-step reduction strategy has been developed
to synthesize a series of bimetallic species with small sizes and
high dispersions onto various metal oxide supports. Superior to other
non-noble metal species, the introduction of Co species can remarkably
and universally promote the catalytic activity of various noble metals
(e.g., Pt, Rh, Ru, and Pd) in AB hydrolysis reactions. The optimized
Pt0.1%Co3%/TiO2 catalyst exhibits
a superhigh H2 generation rate from AB hydrolysis, showing
a turnover frequency (TOF) value of 2250 molH2
molPt
–1 min–1 at
298 K. Such a TOF value is about 10 and 15 times higher than that
of the monometal Pt/TiO2 and commercial Pt/C catalysts,
respectively. The density functional theory (DFT) calculation reveals
that the synergy between Pt and CoO species can remarkably promote
the chemisorption and dissociation of water molecules, accelerating
the H2 evolution from AB hydrolysis. Significantly, the
representative Pt0.25%Co3%/TiO2 catalyst
exhibits excellent stability, achieving a record-high turnover number
of up to 215,236 at room temperature. The excellent catalytic performance,
superior stability, and low cost of the designed catalysts create
new prospects for their practical application in chemical hydrogen
storage.
Cationic framework materials,e specially pure inorganic cationic frameworks that can efficiently and selectively capture harmful heavy metal oxyanions from aqueous solution are highly desired yet scarcely reported. Herein, we report the discovery of a2Dcationic aluminum oxyhydroxide, JU-111, whichsets anew benchmark for heavy metal oxyanion sorbents,especially for Cr VI .Its structure was solved based on 3D electron diffraction tomography data. JU-111 shows fast sorption kinetics (ca. 20 min), high capture capacity (105.4 mg g À1), and broad working pH range (3-10) toward Cr VI oxyanions.U nlike layered double hydroxides (LDHs), which are poorly selective in the presence of CO 3 2À ,J U-111 retains excellent selectivity for Cr VI even under alarge excess of CO 3 2À .These superior features coupled with the ultra-low cost and environmentally benign nature make JU-111 ap romising candidate for toxic metal oxyanion remediation as well as other potential applications.
There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet‐like crystal morphology, large surface area, fully four‐coordinated Al species, and abundant acidic sites. Methanol‐to‐propylene (MTP) tests reveal that the Al‐ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM‐5. FCC tests show that Al‐ITH zeolite is a good candidate as a shape‐selective FCC additive for enhancing propylene and butylene selectivity.
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