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A periodic interaction model with different intercalated anions (X=F,Cl,Br,I,NO 3,OH) is proposed for the CuZnMgAl quaternary hydrotalcites (CuZnMgAl-X).Based on density functional theory,the CuZnMgAl-X geometry was optimized using the CASTEP program.The distribution of anions in the interlayer,and the supra-molecular interaction between host layer and guest anions were investigated by analyzing binding energies,geometric parameters,Mulliken populations,hydrogen-bonding and densities of states.A decreased electronegativity of interlayer anion caused a transfer of charge from guest anions to host layer and a gradual decrease in the strength of electrostatic interaction and hydrogen bonding.The system band gap narrowed,electrons transferred to higher energy levels more easily,and the overall stability of the system decreased.The Cu dopant caused a deviation in CuZnMgAl-X valence band to high energies.Compared with traditional layered double hydroxides,the band gap narrowed and stability decreased,accounting for the difficulty in preparing copper-containing hydrotalcites.

The thiosulfate anion (S2O 3 ) was intercalated into a ZnAl layered double hydroxide (LDH), and its oxidation reaction with hexacyanoferrate(III) (Fe(CN) 36 ) in the confined region between the layers of LDH has been discussed. Based measurements of the intermediate state and final product using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, the oxidation product tetrathionate (S4O 26 ) dissolved in solution, while the reduction product hexacyanoferrate (II) existed in the interlayer of the LDH. Furthermore, the kinetics of this reaction were investigated in batch mode. The influences of the initial Fe(CN) 6 concentration, ZnAl-S2O3 LDH quantity, and reaction temperature on the oxidation reaction were studied. The reaction follows a diffusion-controlled process represented by Crank-Ginstling and Brounstein model with the apparent activation energy of 24.6 kJ·mol-1, which was about 13.7 kJ·mol-1 less than that of the solution reaction under the same conditions. The influence of water content on interlayer spacing was simulated by molecular dynamics. The simulation result shows that the size of this microreactor can be regulated in a certain orientation in the solution environment. From the experimental results and theoretical calculation, we propose a mechanism for the interlayer reaction. This layered material can be used as a novel nano-reactor to regulate the rate of chemical reactions.

A periodic interaction model was proposed for the copper-iron layered double hydroxides, Cu3Fe-LDHs-yH2O (y=0-2). Based on density functional theory, the geometry of Cu3Fe-LDHs-yH2O was optimized using the CASTEP program. The distribution of NO - and H2O in the interlayer and the supermolecular interaction between host and guest was investigated by analyzing the geometric parameters, hydrogen-bonding, charge populations and stepwise hydration energy. Results indicated that when NO - and H2O were inserted into the layers of the Cu3Fe-LDHs, there was a strong supramolecular interaction between the host layer and the guest, including hydrogen-bonding and electrostatic interaction. Hydrogen-bonding was superior to the electrostatic interaction in the hydration process. The strength of hydrogen bonding was ordered as Layer-Anion (L-A) > Anion-Water (A-W) > Layer-Water (L-W) > Water- Water (W-W). In Cu3Fe-LDHs-yH2O, the interlayer distance decreased slightly and then increased significantly with an increase in the number of interlayer water molecules. The Cu―O octahedral forms were stretched gradually because of the increased Jahn-Teller effect of Cu 2+ . The absolute value of the hydration energy decreased gradually with an increase in the number of water molecules. This suggested that the hydration of Cu3Fe-LDHs reached a saturation state. The geometry of Cu3Fe-LDHs-1H2O is close to hexagonal where the metal distortion of the layer is weakest and the stability is strongest; the interlayer distance agrees the experimental value, therefore Cu3Fe-LDHs-1H2O is a stable configuration.

With excellent structural characteristics of layered double hydroxides (LDHs), the high photocatalytic properties of Sn-contained LDHs were synthesized by introducing Sn with photocatalytic activity into the brucite type layers. The obtained LDHs solids were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS) and Brunauer Emmett Teller (BET) surface area analysis, confirming the crystalline phase, molecular structure, photoresponsive properties and specific surface area. Their photocatalytic activities were evaluated by degradation of 4-chlorophenol (4-CP) under visible light. The results showed that ZnSn-LDHs with skeleton structure containing Sn displayed the best decomposition efficiency of 4-CP (about 92.4% removal efficiency, 34.6 mg/g removal amount) under visible light irradiation. In addition, based on the results from gas chromatography (GC) and periodic density functional theory (DFT) analysis, the photocatalytic degradation mechanism and reaction pathway of 4-CP were investigated in detail. The data presented in this study implied that the main decomposition intermediates of 4-CP were hydro- chinone and 4-chloropyrocatechol.