Copper-Based Two-Dimensional Metal-Organic Frameworks for Fenton-like Photocatalytic Degradation of Methylene Blue under UV and Sunlight Irradiation.

To efficiently degrade organic pollutants, photocatalysts must be effective under both ultraviolet (UV) radiation and sunlight. We synthesized a series of new metal-organic frameworks by using mild hydrothermal conditions. These frameworks incorporate three distinct bipyridyl ligands: pyrazine (pyr), 4,4'-bipyridine (bpy), and 1,2-bis(4-pyridyl)ethane (bpe). The resulting compounds are denoted as [Cu(pyz)(H2O)2MF6], [Cu(bpy)2(H2O)2]·MF6, and [Cu(bpe)2(H2O)2]·MF6·H2O [M = Zr (1, 3, and 5) and Hf (2, 4, and 6)]. All six compounds exhibited a two-dimensional crystal structure comprising infinitely nonintersecting linear chains. Compound 3 achieved 100% degradation of methylene blue (MB) after 8 min under UV irradiation and 100 min under natural sunlight in the presence of H2O2 as the electron acceptor. For compound 5, 100% MB degradation was achieved after 120 min under sunlight and 10 min under UV light. Moreover, reactive radical tests revealed that the dominant species involved in photocatalytic degradation are hydroxyl (•OH), superoxide radicals (•O2-), and photogenerated holes (h+). The photodegradation process followed pseudo-first-order kinetics, with photodegradation rate constants of 0.362 min-1 (0.039 min-1) for 3 and 0.316 min-1 (0.033 min-1) for 5 under UV (sunlight) irradiation. The developed photocatalysts with excellent activity and good recyclability are promising green catalysts for degrading organic pollutants during environmental decontamination.

KIn0.33IIITe0.67VITe2IVO7: Zirconolite-like Mixed-Valent Metal Oxide with a 3D Framework.

We provide the material synthesis method, crystal structure information, and characterization of a novel mixed-valent metal oxide KIn0.33IIITe0.67VITe2IVO7, closely related to zirconolite (CaZrTi2O7), a radioactive waste immobilized material, having a 3D framework. The reported metal oxide containing an alkali-metal cation (K+), main-group cation (In3+), tellurate, and tellurite has been synthesized as both single crystals and a pure polycrystalline phase through a hydrothermal synthesis method. Single-crystal X-ray diffraction indicates that KIn0.33Te2.67O7 crystallizing in the orthorhombic space group Cmcm (No. 63) reveals a 3D framework structure with a 1D channel consisting of Te/InO6 octahedra and TeO4 polyhedra. An interesting transition reaction from KIn0.33Te2.67O7 to KIn(TeO3)2 under hydrothermal conditions at 230 °C is discussed.

Conformer specific nonadiabatic reaction dynamics in the photodissociation of partially deuterated thioanisoles (C6H5S-CH2D and C6H5S-CHD2).

In this work, we have investigated nonadiabatic dynamics in the vicinity of conical intersections for predissociation reactions of partially deuterated thioanisole molecules: C6H5S-CH2D and C6H5S-CHD2. Each isotopomer has two distinct rotational conformers according to the geometrical position of D or H of the methyl moiety with respect to the molecular plane for C6H5S-CH2D or C6H5S-CHD2, respectively, as spectroscopically characterized in our earlier report [J. Lee, S.-Y. Kim and S. K. Kim, J. Phys. Chem. A, 2014, 118, 1850]. Since identification and separation of two different rotational conformers of each isotopomer have been unambiguously done, we could interrogate nonadiabatic dynamics of thioanisole in terms of both H/D substitutional and conformational structural effects. Nonadiabatic transition probability, estimated by the experimentally measured branching ratio of the nonadiabatically produced ground-state channel giving C6H5S·(X[combining tilde]) versus the adiabatic excited-state channel leading to the C6H5S·(Ã) radical, shows resonance-like increases at symmetric (νs) or asymmetric (7a) S-CH2D (or S-CHD2) stretching mode excitation in S1 for all conformational isomers of two isotopomers. However, absolute probabilistic value of the nonadiabatic transition is found to vary quite drastically depending on different conformers and isotopomers. The experimental finding that nonadiabatic transition dynamics are very sensitive to subtle changes in the nuclear configuration within the Franck-Condon region induced by the H/D substitution indicates that the S1/S2 conical intersection seam is quite narrowly defined in the multi-dimensional nuclear configurational space as far as the S-methyl predissociation reaction is concerned. In order to understand the relation between molecular structure and nonadiabaticity of reaction, potential energy surfaces near S1/S2 conical intersections have been theoretically calculated along νs and 7a normal mode coordinates for all conformational isomers. Slow-electron velocity map imaging (SEVI) spectroscopy is employed to unravel the extent of intramolecular vibrational redistribution (IVR) for particular mode excitations of S1, providing insights into the dynamic interplay between IVR and nonadiabatic transition probability near the conical intersection seam.

Spectroscopic separation of the methyl internal-rotational isomers of thioanisole isotopomers (C6H5S-CH2D and C6H5S-CHD2).

Two distinct rotational isomers of thioanisole-d1 (C6H5S-CH2D) and thioanisole-d2 (C6H5S-CHD2) with respect to the internal rotation of the methyl moiety have been identified and characterized spectroscopically using the resonantly enhanced two photon ionization, UV-UV hole burning, and slow-electron velocity map imaging techniques. From the statistical weights, the definite assignment for the specific rotational isomer of each isotopomer has been successfully done, providing isomer-specific ionization energies and vibrational frequencies of S1/D0 states. Detailed molecular structures, the methyl internal-rotor barrier, and normal-mode descriptions for selective vibrations are discussed with the aid of density functional theory calculations.

Conical intersection seam and bound resonances embedded in continuum observed in the photodissociation of thioanisole-d3.

Herein, the multi-dimensional nature of the conical intersection seam has been experimentally revealed in the photodissociation reaction of thioanisole-d3 (C6H5SCD3) excited on S1, giving C6H5S·(à or X̃]) +·CD3 products. The translational energy distribution of the nascent·CD3 fragment, reflecting the relative yields of the C6H5S·(Ã) and C6H5S·(X̃) products, was measured at each S1 vibronic band using the velocity map ion imaging technique. Direct access of the reactant flux to the conical intersection seam leads to the increase of the nonadiabatic transition probability resulting in sharp resonances in the X̃/ÃC6H5S·product branching ratio at several distinct S1 vibronic bands. The nature of the S1 vibronic bands associated with such dynamic resonances was clarified by the mass-analyzed threshold ionization spectroscopy. The bound state embedded in continuum generated by the conical intersection is observed as a distinct dynamic resonance, revealing the nature of the nuclear motion responsible for the nonadiabatic coupling of two potential energy surfaces at the conical intersection. The multi-dimensional facets of the conical intersection seam in terms of its detailed structure and dynamic role are discussed with the aid of theoretical calculations.

Valence electron ionization dynamics of chromium by a photoelectron imaging technique: J+-dependent state and angular distribution.

The photoionization of Cr at excited states is investigated using a velocity-map photoelectron imaging technique. Benzene chromium carbonyl or bis(η(6)-benzene) chromium was used as a precursor for the generation of excited Cr atoms. The a (5)S2 → x (5)P°3 and a (5)D3 → y (5)D°2 transitions are then employed for the preparation of resonant intermediate states in a two-color two-photon ionization process, in which an electronic configurational change from 3d(4)((5)D)4s4p((1)P°) to 3d(4)4s((6)D(J+)) occurs. The photoelectron kinetic energy distribution is found to be very sensitive to the ionization energy and the total angular momentum quantum number of the chromium ion (J(+)). Anisotropy parameters associated with departing electrons also show significant variation depending on the energy and total angular momentum quantum number, suggesting that direct and/or indirect ionization should be quantum-mechanically mixed, manifesting the complicated nature of angular momentum couplings in the ionization continuum.

Nuclear motion captured by the slow electron velocity imaging technique in the tunnelling predissociation of the S1 methylamine.

Predissociation dynamics of methylamines (CH(3)NH(2) and CH(3)ND(2)) on the first electronically excited states are studied using the slow-electron velocity imaging method to unravel the multi-dimensional nature of the N-H(D) chemical bond dissociation reaction which occurs via tunnelling. The nearly free internal rotation around the C-N bond axis is found to be strongly coupled to the reaction pathway, revealing nuclear motions actively involved in the tunnelling process on the S(1) potential energy surfaces. The vibrational state-resolved energy and angular distributions of photoelectron, ejected from the ionization mediated by the metastable intermediate S(1) state provide a unique way for mapping the predissociative potential energy surfaces.

Synchrotron-based high-resolution photoemission spectroscopy study of ZIRLO cladding with H2O adsorption: Coverage and temperature dependence.

The coverage and temperature dependence of ZIRLO cladding with H2O adsorption are studied using synchrotron-based high-resolution photoemission spectroscopy (HRPES). Based on the analytical results of the Zr 3d, O 1 s, C 1 s, and Sn 3d HRPES profiles prior to H2O adsorption, we determine the surface compositions of O2-, hydroxyl OH-, chemisorbed H2O, zirconium carbide, adventitious carbon, Sn metal, and SnO2 in ZIRLO. When ZIRLO is exposed to H2O molecules, the relative proportion of zirconium metal decreases, whereas that of the total zirconium oxides increases, suggesting the reaction between H2O and the zirconium metal in ZIRLO. On annealing a sample with 1000 L H2O on ZIRLO at 300 °C, Zr2O3 and ZrO2 decompose, and oxygen diffuses into the bulk, thereby reducing the oxidation states of zirconium on the surface. Moreover, at this temperature, the excess H2O molecules on ZIRLO are thoroughly desorbed and tin element is diffused into the bulk in ZIRLO.

State-selective predissociation dynamics of methylamines: the vibronic and HD effects on the conical intersection dynamics.

The photodissociation dynamics of methylamines (CH(3)NH(2) and CD(3)ND(2)) on the first electronically excited state has been investigated using the velocity map ion imaging technique probing the H or D fragment. Two distinct velocity components are found in the H(D) translational energy distribution, implying the existence of two different reaction pathways for the bond dissociation. The high H(D) velocity component with the small internal energy of the radical fragment is ascribed to the N-H(D) fragmentation via the coupling of S(1) to the upper-lying S(2) repulsive potential energy surface along the N-H(D) bond elongation axis. Dissociation on the ground S(0) state prepared via the nonadiabatic dynamics at the conical intersection should be responsible for the slow H(D) fragment. Several S(1) vibronic states of methylamines including the zero-point level and nnu(9) states (n=1, 2, or 3) are exclusively chosen in order to explore the effect of the initial quantum content on the chemical reaction dynamics. The branching ratio of the fast and slow components is found to be sensitive to the initial vibronic state for the N-H bond dissociation of CH(3)NH(2), whereas it is little affected in the N-D dissociation event of CD(3)ND(2). The fast component is found to be more dominant in the translational distribution of D from CD(3)ND(2) than it is in that of H from CH(3)NH(2). The experimental result is discussed with a plausible mechanism of the conical intersection dynamics.