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Mei-Tsan Kuo, Kaito Takahashi,* and Jim Jr-Min Lin*
ChemPhysChem
Reactions of Criegee Intermediates are Enhanced by Hydrogen-atom Relay Through Molecular Design
We report a type of highly efficient double hydrogen atom transfer (DHAT) reaction. The reactivities of 3-aminopropanol and 2-aminoethanol towards Criegee intermediates (syn- and anti-CH3CHOO) were found to be much higher than those of npropanol and propylamine. Quantum chemistry calculation has confirmed that the main mechanism of these very rapid reactions is DHAT, in which the nucleophilic attack of the NHgroup is catalyzed by the OH group which acts as a bridge of HAT. Typical gas-phase DHAT reactions are termolecular reactions involving two hydrogen bonding molecules; these reactions are typically slow due to the substantial entropy reduction of bringing three molecules together. Putting the reactive and catalytic groups in one molecule circumvents the problem of entropy reduction and allows us to observe the DHAT reactions even at low reactant concentrations. This idea can be applied to improve theoretical predictions for atmospherically relevant DHAT reactions.
Ting Zhou, Lei Wang, Xingye Huang, Junjuda Unruangsri, Hualei Zhang, Rong Wang, Qingliang Song, Qingyuan Yang, Weihua Li, Changchun Wang, Kaito Takahashi,* Hangxun Xu,* and Jia Guo*
Nature Communications, 12, 3934-
PEG-stabilized coaxial stacking of two-dimensional covalent organic frameworks for enhanced photocatalytic hydrogen evolution
Two-dimensional covalent organic frameworks (2D COFs) featuring periodic frameworks, extended π-conjugation and layered stacking structures, have emerged as a promising class of materials for photocatalytic hydrogen evolution. Nevertheless, the layer-by-layer assembly in 2D COFs is not stable during the photocatalytic cycling in water, causing disordered stacking and declined activity. Here, we report an innovative strategy to stabilize the ordered arrangement of layered structures in 2D COFs for hydrogen evolution. Polyethylene glycol is filled up in the mesopore channels of a β-ketoenamine-linked COF containing benzothiadiazole moiety. This unique feature suppresses the dislocation of neighbouring layers and retains the columnar π-orbital arrays to facilitate free charge transport. The hydrogen evolution rate is therefore remarkably promoted under visible irradiation compared with that of the pristine COF. This study provides a general post-functionalization strategy for 2D COFs to enhance photocatalytic performances.
Pornsawan Sikam, Kaito Takahashi, Thantip Roongcharoen, Thanadol Jitwatanasirikul, Chirawat Chitpakdee, Kajornsak Faungnawakij, Supawadee Namuangruk*
Applied Surface Science
Effect of 3d-transition metals doped in ZnO monolayers on the CO2 electrochemical reduction to valuable products: first principles study
CO2 conversion to valuable products on ZnO (0001) monolayer doped by transition metals (TM-ZnO where TM is Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) was investigated by density functional theory calculation. The results show that doping TMs can reduce the overpotential for CO2 reduction reaction (CRR) compared to pristine ZnO. Significantly, the oxidation state of TMs by different d-orbital occupancy results in a change of the electronic properties of the catalysts, leading to a difference in reactivity, reaction pathway, and selectivity of the final products. Early TMs (Sc to Cr) showing oxidation state 3+ prefer CH4 as a product while late TMs (Mn to Cu) showing oxidation state 2+ can make HCOOH. Remarkably, Co-ZnO can produce HCOOH with ultra-low overpotential at 0.02 V and can further produce CH3OH with an overpotential of only 0.45 V. Therefore, Co-ZnO monolayer is suggested as a promising CRR catalyst for experimental research. This work sheds light on the rational design of low-cost metal oxides with high stability, activity, and product selectivity for CRR and other reactions.
Wikorn Punyain, and Kaito Takahashi*
Physical Chemistry Chemical Physics
Evaluation of Ar tagging toward the vibrational spectra and zero point energy of X-HOH, X-DOH, and X-HOD, for X=F, Cl, Br
In this study, we theoretically evaluated the effect of argon tagging toward the binding energy and vibrational spectra of water halide anion complexes, Ar.X-HOH, Ar.X-HOD, and Ar.X-DOH (X=F, Cl, Br). The ionic hydrogen bonded (IHB) OH stretching mode was calculated to have a strong peak in the vibrational spectra, and coupling to intermolecular modes as well as bending modes was observed as combination bands and Fermi resonances. We found that the argon tagging affected the IHB OH stretching peak position in Ar.F-H2O, but not in Ar.Cl-H2O and Ar.Br-H2O. Furthermore, D-binding is favored for Cl and Br based on zero point energies, but for F, our calculated zero point energies did not show a preference between H- and D-binding. We show that the competition of the energy lowering in the zero point energy of the anharmonic IHB OH (OD) stretching mode versus the intermolecular out-of-plane IHB OH (OD) wagging mode is important for determining the preference between H- and D-binding for these monohydrated halide clusters. We also found that for X-HOD, the HOD bending fundamental peak is blue shifted compared to bare HOD, but is redshifted for F-DOH.  
Kaito Takahashi
Chinese Journal of Chemical Physics, 33, 13-22
Experimental vibrational spectra of heavy light XH stretching vibrations of simple molecules have been analyzed using the local mode model. In addition, the bond dipole approach, which assumes that the transition dipole moment (TDM) of the XH stretching mode is aligned along the XH bond, has helped analyze experimental spectra. We performed theoretical calculations of the XH stretching vibrations of HOD, HND-, HCD, HSD, HPD-, and HSiD using local mode model and multi-dimensional normal modes. We found that consistent with previous notions, a localized 1D picture to treat the XH stretching vibration is valid even for analyzing the TDM tilt angle. In addition, while the TDM of the OH stretching fundamental transition tilted away from the OH bond in the direction away from the OD bond, that for the XH stretching fundamental of HSD, HND-, HPD-, HCD, and HSiD tilted away from the OH bond but toward the OD bond. This shows that bond dipole approximation may not be a good approximation for the present systems and that the heavy atom X can affect the transition dipole moment direction. The variation of the dipole moment was analyzed using the atoms-in-molecule method.
Journal of Physical Chemistry Letters, 9, 7040-7044.
Criegee Intermediate Reaction with Alcohol Is Enhanced by a Single Water Molecule
The role of water in gas phase reactions has gained considerable interests. Here we report a direct kinetic measurement of the reaction of syn-CH3CHOO (a Criegee intermediate or carbonyl oxide) with methanol at various relative humidity (RH = 0-80%) under near ambient conditions (298 K, 250-755 Torr). The data indicate that a single water molecule expedites the reaction by upto a factor of 3. The rate coefficient of the corresponding reaction, syn-CH3CHOO + CH3OH + H2O ® products, has been determined to be (1.95 ± 0.11) x 10-32 cm6 s-1 at 298 K with no observable pressure dependence for 250-755 Torr. Quantum chemistry calculation shows that the dominating pathway involves a hydrogen-bonded ring structure, in which methanol is donating a hydrogen atom to water; water is donating a hydrogen atom to the terminal oxygen atom of the Criegee intermediate; on the product side, H2O is reformed and acts as a catalyst.
 
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