Effects of Calcination Condition on the Network Structure of Triethoxysilane (TRIES) and How Si–H Groups Influence Hydrophobicity Under Hydrothermal Conditions

Network size control was evaluated for microporous membranes derived from triethoxysilane (TRIES) that contains highly reactive Si–H groups. It was possible to control the concentration of the Si–H groups via the conditions of calcination (temperature, atmosphere). Si–H groups remained within their network structure when the TRIES membrane was calcined at 350 °C under a N2 atmosphere, and had a loose network structure (H2 permeance: 5.40 × 10–7 mol m–2 s–1 Pa–1, H2/CH4 selectivity: 36). When calcination at high temperatures converted the Si–H groups to Si–O–Si groups, the TRIES membrane showed a high level of separation performance (H2 permeance: 2.34 × 10–7 mol m–2 s–1 Pa–1, H2/CH4 selectivity: 590) due to a densification of the network structure. Compared with conventional microporous silica membranes, a TRIES membrane with Si–H groups showed hydrophobic properties, but water vapor was adsorbed and/or capillary-condensed in the microporous structure, and permeation blocking for He molecules was observed at temperatures below 150 °C in the presence of saturated water vapor at 25 °C. Hydrophobic Si–H groups improved the hydrothermal stability at 300 °C, but depending on the partial pressure of the steam, the reaction between Si–H groups and water vapor degraded the hydrothermal stability of the TRIES membranes

A Photocatalytic System Composed of Benzimidazolium Aryloxide and Tetramethylpiperidine 1‑Oxyl to Promote Desulfonylative α‑Oxyamination Reactions of α‑Sulfonylketones

A new photocatalytic system was developed for carrying out desulfonylative α-oxyamination reactions of α-sulfonylketones in which α-ketoalkyl radicals are generated. The catalytic system is composed of benzimidazolium aryloxide betaines (BI+–ArO–), serving as visible light-absorbing electron donor photocatalysts, and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), playing dual roles as an electron donor for catalyst recycling and a reagent to capture the generated radical intermediates. Information about the detailed nature of BI+–ArO– and the photocatalytic processes with TEMPO was gained using absorption spectroscopy, electrochemical measurements, and density functional theory calculations

Visible Light and Hydroxynaphthylbenzimidazoline Promoted Transition-Metal-Catalyst-Free Desulfonylation of <i>N-</i>Sulfonylamides and <i>N-</i>Sulfonylamines

A visible light promoted process for desulfonylation of <i>N-</i>sulfonylamides and -amines has been developed, in which 1,3-dimethyl-2-hydroxynaphthyl­benzimidazoline (HONap-BIH) serves as a light absorbing, electron and hydrogen atom donor, and a household white light-emitting diode serves as a light source. The process transforms various <i>N-</i>sulfonylamide and -amine substrates to desulfonylated products in moderate to excellent yields. The observation that the fluorescence of 1-methyl-2-naphthoxy anion is efficiently quenched by the substrates suggests that the mechanism for the photoinduced desulfonylation reaction begins with photoexcitation of the naphthoxide chromophore in HONap-BIH, which generates an excited species via intramolecular proton transfer between the HONap and BIH moieties. This process triggers single electron transfer to the substrate, which promotes loss of the sulfonyl group to form the free amide or amine. The results of studies employing radical probe substrates as well as DFT calculations suggest that selective nitrogen–sulfur bond cleavage of the substrate radical anion generates either a pair of an amide or amine anion and a sulfonyl radical or that of an amidyl or aminyl radical and sulfinate anion, depending on the nature of the <i>N-</i>substituent on the substrate. An intermolecular version of this protocol, in which 1-methyl-2-naphthol and 1,3-dimethyl-2-phenyl­benzimidazoline are used concomitantly, was also examined