Selectivity

Abstract: This work exploited amine steric hindrance effect to developing next-generation CO2-selective facilitated transport membranes for H2 purification for fuel cells. The new membrane was synthesized by incorporating moderately hindered poly-N-isopropylallylamine as a fixed-site carrier along with mobile carriers into cross-linked polyvinylalcohol-poly(siloxane) network. The new membrane exhibited high CO2 permeability of greater than 6500 Barrers, CO2/H2 selectivity of more than 300, and CO2/N2 selectivity of at least 650 at 110 °C and a feed pressure of 2 atm. Better membrane separation results were achieved as the sweep-side water content was increased. The membrane also showed good stability of at least 430 h at 110 °C and 2 atm. The membrane performance reduced as temperature was increased from 107 to 180 °C as a result of the reduction of water retention ability of the membrane; however, it still held a good CO2/H2 selectivity of about 34 at 180 °C.

Abstract: The effect of the nature of the crosslinking agents in template-imprinted polymers on the selectivity during racemic resolution was investigated Ethylene dimethacrylate was found to be the best crosslinking agent The highest selectivity was achieved with polymers which have been prepared with 70-95% crosslinking agent in the monomeric mixture A new optically active crosslinking agent, 1,4;3,6-dianhydro-D-sorbitol 2,5-dimethacrylate, was synthesized and was used for the preparation of template-imprinted polymers Interpenetrating networks consisting of two different crosslinking systems did not bring about any significant improvement in selectivity for racemic resolution A strong temperature effect for racemic resolution was observed; an ethylene dimethacrylate-crosslinked, template-imprinted polymer showed an optimum selectivity at 75°C with a ratio of distribution coefficients of the D- and L-isomers of α = 4,56 for the separation of the racemate of the template

Abstract: Rapid and sensitive detection of Ag+ in aquatic ecosystems is of great significance for public health and environmental security. In this report, a simple and feasible colorimetric method for the detection of Ag+ at an ultralow concentration is developed. Bovine serum albumin stabilized gold nanoclusters (BSA@AuNCs) possess the peroxidase-like activity that could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2. Once Ag+ is introduced, Ag+ selectively reacts with Au° through redox reaction, which induces an apparent inhibition of the peroxidase-like activity of BSA@AuNCs. On the basis of this effect, a colorimetric Ag+ sensor is established. The high specificity of the Ag–Au interaction provides excellent selectivity over the interfering metal ions. The lowest detectable concentration for Ag+ is 0.204 μM. And this method could be applied for the rapid analysis of Ag+ in lake water with satisfactory results. These advantages demonstrate that the proposed method is a promising candidate for the detection of Ag+ in water samples.

Abstract: Iridium- and ruthenium-free approaches to protected allylic amines and alkyl nitriles under photoredox conditions are reported. An inexpensive organic dye, eosin Y, catalyzes coupling of Boc-protected potassium α-aminomethyltrifluoroborates with a variety of substituted alkenyl sulfones through an α-aminomethyl radical addition–elimination pathway. Allylic and homoallylic amines were formed in moderate yields with high E/Z selectivity. The mechanistic approach was extended using tosyl cyanide as a radical trap, enabling the conversion of alkyltrifluoroborates to nitriles via a Fukuzumi acridinium-catalyzed process.