Porous heterogeneous catalysts play a pivotal role in the chemical industry. Herein a new Hf-based metal-organic framework (Hf-NU-1000) incorporating Hf6 clusters is reported. It demonstrates high catalytic efficiency for the activation of epoxides, facilitating the quantitative chemical fixation of CO2 into five-membered cyclic carbonates under ambient conditions, rendering this material an excellent catalyst. As a multifunctional catalyst, Hf-NU-1000 is also efficient for other epoxide activations, leading to the regioselective and enantioretentive formation of 1,2-bifuctionalized systems via solvolytic nucleophilic ring opening.
Potentiometric acid–base titration is introduced as a method to evaluate pKa values (Brønsted acidity) of protons present in the nodes of water stable Zr6- and Hf6-based metal–organic frameworks (MOFs), including UiO-type MOFs, NU-1000, and MOF-808.
The synthesis of nano-sized particles of NU-1000 (length from 75 nm to 1200 nm) and PCN-222/MOF-545 (length from 350 nm to 900 nm) is reported. The catalytic hydrolysis of methyl paraoxon was investigated as a function of NU-1000 crystallite size and a significant enhancement in the rate was observed for the nano-sized crystals compared to microcrystals.
Seven Zr/Hf-based MOFs with different degrees of defects were obtained by modulating the synthetic conditions. The number of missing linkers in these MOFs was calculated based on potentiometric acid-base titration. The number of defects was found to correlate quantitatively with the catalytic activity of UiO-type MOFs for an acid-catalyzed epoxide ring-opening reaction. More importantly, we were able to identify a MOF with inherent defective Zr6 nodes, which showed great activity and regio-selectivity for the epoxide ring-opening reaction.
Thin films of the metal-organic framework (MOF) NU-1000 were grown on conducting glass substrates. The films uniformly cover the conducting glass substrates and are composed of free-standing sub-micrometer rods. Subsequently, atomic layer deposition (ALD) was utilized to deposit Co(2+) ions throughout the entire MOF film via self-limiting surface-mediated reaction chemistry. The Co ions bind at aqua and hydroxo sites lining the channels of NU-1000, resulting in three-dimensional arrays of separated Co ions in the MOF thin film. The Co-modified MOF thin films demonstrate promising electrocatalytic activity for water oxidation.
AML1/ETO results from the t(8;21) associated with 12%-15% of acute myeloid leukemia. The AML1/ETO MYND domain mediates interactions with the corepressors SMRT and N-CoR and contributes to AML1/ETO's ability to repress proliferation and differentiation of primary bone marrow cells as well as to enhance their self renewal in vitro. We solved the solution structure of the MYND domain and show it to be structurally homologous to the PHD and RING finger families of proteins. We also determined the solution structure of an MYND-SMRT peptide complex. We demonstrated that a single amino acid substitution that disrupts the interaction between the MYND domain and the SMRT peptide attenuated AML1/ETO's effects on proliferation, differentiation, and gene expression.
The combination (AIM-ME) of atomic
layer deposition in metal–organic
frameworks (MOFs) and metal exchange (ME) is introduced as a technique
to install dispersed metal atoms into the mesoporous MOF, NU-1000.
Zn-AIM, which contains four Zn atoms per Zr6 node, has
been synthesized through AIM and further characterized through density
functional calculations to provide insight into the possible structure.
Zn-AIM was then subjected to modification via transmetalation to yield
uniform porous materials that present nonstructural Cu, Co, or Ni
atoms.
The rapid destruction of chemical threats such as phosphate-based nerve agents is of considerable current interest. The hydrolysis of the nerve-agent simulant methylparaoxon, as catalysed by UiO-66 and UiO-67, was examined as a function of pH. Surprisingly, even though typical phosphate-ester hydrolysis mechanisms entail nucleophilic attack of the simulant by aqueous hydroxide, the rate of hydrolysis accelerates as the solution pH is lowered. The unexpected behavior is attributed to a pH-dependent composition change followed by ligand substitution at the Zr 6 -based node.
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