Nitrogen-doped carbon catalysts prepared from amino-functionalized metal–organic frameworks [amino-MIL-101­(Al)] were investigated for the oxygen-reduction reaction (ORR) with special emphasis on elucidating the role of different nitrogen species (e.g., pyridinic, pyrrolic, and quaternary N) as active catalytic sites. Careful optimization of pyrolysis temperature of the amino-MIL-101­(Al) leveraged the synthesis of the catalysts with or without quaternary N functionalities. This allowed us to investigate the type(s) of N species responsible for the ORR catalysis and thus address the conflicting results reported so far regarding the pyridinic and/or quaternary N as active sites for ORR catalysis via four-electron transfer (4e–) pathways. Our findings suggest that the total nitrogen content in the catalysts does not influence the ORR, while the quaternary N sites exclusively catalyze the reduction of O2 via the 4e– transfer pathway in both alkaline and acidic electrolytes. Catalysts containing only pyridinic and pyrrolic N were observed to be ineffective for the ORR. The experimental results were further supported by computational simulation using the gradient–correlated density functional theory which revealed that the dissociative O2 adsorption (i.e., binding and cleavage of OO bonds) is more favorable to quaternary N. Furthermore, calculations based on the relative surface potential energy, dipole moment, binding energy, and electron density indicate that the most stable structure of O2 chemisorption sites could only be achieved on the quaternary N carbon.

The adsorptions of HOCl on ice surface were studied with the help of QM/EFP scheme. HOCl binding energies were predicted to be −12.2 to −17.8 kcal/mol (BSSE corrected values) depending on surface absorption sites. These values are much larger than previous quantum mechanical estimations but are rather in good agreements with experiments and MD study. Structurally, various new surface binding configurations of HOCl, including an unusual penta coordination, were found indicating diverse reacting environments of ice surface. In general, it was found that the ice surface itself as well as HOCl adsorptions are strongly affected by long-range electrostatics, surface heterogeneity and hydrogen disorders of bulk ice, revealing the unique characteristics of ice surface as a reacting environment. As a way of modeling ice surface, we demonstrated that the hybrid QM/EFP scheme is very effective.

A visible-light-induced synthesis of N-H carbazoles from easily accessible 2,2'-diaminobiaryls in the absence of any external photosensitizer is reported. The process only requires BuONO and natural resources, visible light, and molecular oxygen for the synthesis of N-H carbazoles. Experimental and computational studies support that the in situ formation of a visible-light-absorbing photosensitizing intermediate, benzocinnoline N-imide, is responsible for the activation of triplet molecular oxygen to singlet oxygen that, in turn, promotes the synthesis of carbazole.

Adsorptions of formic (FA) and acetic acids (AA) on I h ice surface were studied using quantum mechanical/ effective fragment potential (QM/EFP) scheme. Contrasting to the earlier studies in which trans-conformers were found as major surface configurations, our QM/EFP models found various cisand trans-conformers on ice surfaces with the cis-conformers being more stable. The surface binding energies and configurations were largely dependent on surface heterogeneity yielding the various surface conformers. In addition, the overall binding energies of acetic acid are slightly higher as compared to formic acid, implying the stabilization effect of methyl group. Our study also found a feasible deprotonation route of adsorbed transformic acid. In contrast, acetic acid prefers molecular form due to the unfavorable hydrophobic methyl group. Therefore it is interesting to note that the additional methyl group of acetic acid enhances surface binding energies. But at the same time it reduces the chance of its deprotonation. Our ice model clearly demonstrated the significant effects of intrinsic surface heterogeneity on the distributions of surface binding energies and configurations, which cannot be represented by small water clusters.

The interaction of sulfur dioxide (SO 2 ) gas with a crystalline ice surface at low temperature was studied by analyzing the surface species with low energy sputtering (LES) and reactive ion scattering methods and the desorbing gases with temperatureprogrammed desorption mass spectrometry. The study gives direct evidence for the occurrence of efficient hydrolysis of SO 2 with low energy barriers on the ice surface. Adsorbed SO 2 molecules react with the ice surface at temperatures above ∼90 K to form anionic molecular species, which can be detected by OH − , SO 2 − , and HSO 3 − emission signals in the LES experiments. Heating the sample above ∼120 K causes the desorption of SO 2 gas from the surface-bound hydrolysis products. As a result, the hydrolysis of SO 2 on an ice surface is most efficient at 100− 120 K. The surface products formed at these temperatures correspond to metastable states, which are kinetically isolated on the cold surface. Quantum mechanical calculations of a model ice system suggest plausible mechanistic pathways for how physisorbed SO 2 is transformed into chemisorbed HSO 3 − species. HSO 3 − is formed either by direct conversion of physisorbed SO 2 or through the formation of a stable H 2 SO 3 surface complex, both involving proton transfer on the ice surface with low energy barriers. These findings suggest the possibility that thermal reactions of SO 2 occur efficiently on the ice surface of Jovian satellites even without bombardment by high-energy radiation.