Steric bulk controls CO(2) absorption: N-substituted amino acid salts in poly(ethylene glycol) reversibly absorb CO(2) in nearly 1:1 stoichiometry. Carbamic acid is thought to be the absorbed form of CO(2); this was supported by NMR and in situ IR spectroscopy, and DFT calculations. The captured CO(2) could be converted directly into oxazolidinones and thus CO(2) desorption could be sidestepped.
Sterischer Anspruch kontrolliert CO2‐Absorption: N‐substituierte Aminosäuresalze in Poly(ethylenglycol) absorbieren reversibel CO2 mit einem stöchiometrischen Verhältnis von fast 1:1. Carbaminsäure wird als die absorbierte Form von CO2 vermutet, was durch NMR‐ und In‐situ‐IR‐Spektroskopie sowie DFT‐Rechnungen untermauert wird. Das aufgenommene CO2 kann direkt in Oxazolidinone überführt werden, um so eine CO2‐Desorption zu vermeiden.
Asymmetric olefin isomerization of β,γ- to α,β-unsaturated butenolides catalyzed by novel cinchona alkaloid derivatives was investigated in-depth using density functional theory (M05-2x and B2PLYP-D). Three possible mechanistic scenarios, differing in the binding modes of the substrate to the catalyst, have been evaluated. Computations revealed that both the protonated quinuclidine and the 6'-OH of catalysts may act as the proton donor in the stereocontrolling step. Variation of the catalytic activity and enantioselectivity by tuning the electronic effect of catalyst was well reproduced computationally. It suggested that, for certain acid-base bifunctional chiral catalysts, the acid-base active sites of catalysts may interconvert and give new catalyst varieties of higher activity and selectivity. In addition, the noncovalent interactions in the stereocontrolling transition-state structures were identified, and their strength was quantitatively estimated. The weak nonconventional C-H···O hydrogen-bonding interactions were found to be crucial to inducing the enantioselectivity of the cinchona alkaloid derivatives catalyzed asymmetric olefin isomerization. The computational results provided further theoretical evidence that the rate-limiting step of this bioinspired organocatalytic olefin isomerization is inconsistent with that of the enzyme catalyzed olefin isomerization.
Recently,
the development of nanozymes with high catalytic performance
is gaining more and more attention due to the ever-growing demands
for their practical applications. The elaborate design of its morphology
has demonstrated to be an effective approach to improve the performance
of these nanozymes. Herein, a hybrid of iron disulfide nanoparticles
(FeS2 NPs) encapsulated by two-dimensional (2D) carbon
nanosheets (NSs), denoted as FeS2@C NSs, demonstrates both
superior peroxidase-like activity and excellent stability. The incorporation
of 2D carbon sheets endows the proposed FeS2@C nanozymes
with high specific surface area, providing abundant active sites to
facilitate the contact with substrates. Moreover, the embedded FeS2 NPs are kept from aggregation due to the encapsulation and
confinement of 2D carbon sheets, avoiding the conventional failure
of single-component nanozymes. Based on glucose oxidase (GOx) and
the elaborately designed FeS2@C nanozymes, a colorimetric
method for glucose detection is then developed with excellent simplicity
and sensitivity. The detection limit of the sensing platform is as
low as 0.19 μM for a glucose assay. More notably, this method
can be successfully employed for the glucose assay in some real samples,
indicating the great potential of this FeS2@C NS-based
nanozymes in the fields of biotechnology and clinical diagnostics.
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