A novel functionalized MOF material, Brönsted acidic ionic liquid (BAIL) confined inside well-defined MIL-101 nanocages, was developed for the first time based on the tandem post-synthetic strategy. The catalytic performance of BAIL confined in MIL-101 material was evaluated by using the acetalization of benzaldehyde with glycol as a probe reaction. The resulting BAIL/MIL-101 material exhibited superior catalytic performance, which is mainly due to the combination of the advantageous merits of ionic liquid catalyst with the desirable microenvironment in the MIL-101 nanocages.

In this paper, the excited-state intramolecular proton transfer (ESIPT) process and the solvatochromic effect of 2-(4-(diethylamino)phenyl)-3-hydroxy-4H-chromen-4-one (DHC) molecules were reported by the density functional theory and time-dependent density functional theory method. We optimized the structures in four kinds of solvents, and the recorded absorption and fluorescence spectra were in agreement with the experiments. By establishing the potential energy curve, we proved that this fluorescent probe was designed based on the ESIPT process of the parent molecule DHC. A deeper study of the ESIPT process revealed that the energy consumed by the molecules along the C5–C18 bond twist was an important part of the dual fluorescence characteristics of the DHC, and the geometric structure tended to be planar with the decrease of the dielectric constant of the solvent. The effect of solvent media on electronic transition energies and absorption as well as florescence spectra were presented. As we know, a driving force of the proton transfer reaction was provided by hydrogen bonding. By comparing the infrared vibration spectrum, bond length and bond angle, we found that the hydrogen bond was enhanced after photoexcitation and was gradually increased as the solvent dielectric constant decreased (dimethylsulfoxide (DMSO) < acetonitrile (ACN) < dichloromethane (DCM) < 1,4-dioxane (DIO)), which was also evidenced by the reduced density gradient function (RDG) isosurface and scatter plots. Therefore, the process of ESIPT reaction was controlled by the solvent. Furthermore, the effect of the solvent on ESIPT was explained by comparing the reaction energy barrier in four kinds of solvents. The results showed that ESIPT was more likely to occur as the solvent dielectric constant decreased.

The inhibition performance and mechanism of nicotinic acid (NA), nicotinic acid amide (NAA) and 4-methoxypyridine (MP) for the corrosion of mild steel in 0.5 M HCl solution were investigated and compared by means of experimental tests, including potentiodynamic polarization and electrochemical impedance spectroscopy measurements, surface analyses and quantum chemistry calculation. The electrochemical results show that the inhibition efficiencies of the three inhibitors increase with the concentration and decrease with the temperature. The NAA and MP inhibitors exhibit the highest and lowest efficiency and activation energy for the corrosion process, respectively, which is confirmed by the corrosion morphology observation. Fourier transform infrared analysis and X-ray photoelectron spectroscopy (XPS) analysis confirm the spontaneous adsorption of all three inhibitors on the surface. The adsorption analysis demonstrates that the adsorption process follows Langmuir model and consists of both physisorption and chemisorption. The quantum chemistry calculation correlates the molecular structures and charge density distributions with the corrosion inhibition efficiencies of NAA, NA and MP inhibitors, and further proves that the good inhibition performance of NAA inhibitor originates its high adsorption ability.