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Several reactions, known from other amine systems for CO2 capture, have been proposed for Lewatit R VP OC 1065. The aim of this molecular modeling study is to elucidate the CO2 capture process: the physisorption process prior to the CO2-capture and the reactions. Molecular modeling yields that the resin has a structure with benzyl amine groups on alternating positions in close vicinity of each other. Based on this structure, the preferred adsorption mode of CO2 and H2O was established. Next, using standard Density Functional Theory two catalytic reactions responsible for the actual CO2 capture were identified: direct amine and amine-H2O catalyzed formation of carbamic acid. The latter is a new type of catalysis. Other reactions are unlikely. Quantitative verification of the molecular modeling results with known experimental CO2 adsorption isotherms, applying a dual site Langmuir adsorption isotherm model, further supports all results of this molecular modeling study.

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Cation exchange is a powerful tool for the synthesis of nanostructures such as core–shell nanocrystals, however, the underlying mechanism is poorly understood. Interactions of cations with ligands and solvent molecules are systematically ignored in simulations. Here, we introduce the concept of pseudoligands to incorporate cation-ligand-solvent interactions in molecular dynamics. This leads to excellent agreement with experimental data on cation exchange of PbS nanocrystals, whereby Pb ions are partially replaced by Cd ions from solution. The temperature and the ligand-type control the exchange rate and equilibrium composition of cations in the nanocrystal. Our simulations reveal that Pb ions are kicked out by exchanged Cd interstitials and migrate through interstitial sites, aided by local relaxations at core–shell interfaces and point defects. We also predict that high-pressure conditions facilitate strongly enhanced cation exchange reactions at elevated temperatures. Our approach is easily extendable to other semiconductor compounds and to other families of nanocrystals.

The X-ray structures and spectroscopic and magnetic properties of [tetrakis(&mgr;-1-phenylcyclopropane-1-carboxylato-O,O')bis(ethanol-O)dicopper(II)], 1, and catena-poly[[bis(&mgr;-diphenylacetato-O:O')dicopper](&mgr;(3)-diphenylacetato-1-O:2-O':1'-O')(&mgr;(3)-diphenylacetato-1-O:2-O':2'-O')], 2, two extended-chain copper(II) carboxylates with dinuclear paddle-wheel subunits, are reported. 1 crystallizes in the triclinic space group P&onemacr;, with a = 6.8873(3) Å, b = 11.7367(6) Å, c = 13.7899(7) Å, alpha = 107.076(4) degrees, beta = 93.545(4) degrees, gamma = 103.967(4) degrees, Z = 1. The Cu.Cu distance is 2.6009(4) Å, and the Cu.carboxylate O distances are in the range 1.937(2)-1.962(2) Å. The ethanol at the apex forms an unsymmetrical bifurcated H bond to two carboxylate oxygens of another dinuclear unit with O.O distances 2.980(3) and 3.108(3) Å, thereby extending the structure along the a-axis. The magnetic structure consists of isolated antiferromagnetically coupled dinuclear copper units, with a -2J value of 242 cm(-)(1), in concurrence with the EPR parameters, viz., g(x)() = 2.03(1), g(y)() = 2.07(1), g(z)() = 2.35(1), A( parallel) = 0.064(2) cm(-)(1), D = 0.316(15) cm(-)(1), E = 0.005(1) cm(-)(1). The -2J value is the smallest value measured for dinuclear copper carboxylates with oxygen-donor ligands at the axial position and no electron-withdrawing carboxylate R groups. 2 crystallizes in the monoclinic space group P2(1)/c, with a = 15.953(2) Å, b = 5.385(6) Å, c = 28.322(10) Å, beta = 120.22(3) degrees, Z = 2. The compound contains tetrakis(diphenylacetato)dicopper(II) units, forming a polymeric structure along the b-axis by axial coordination of a carboxylate oxygen to copper of a subsequent dinuclear unit, at 2.323(11) Å. The intradimer Cu.Cu distance is 2.594(4) Å; the interdimer Cu.Cu distance is 3.425(5) Å. The -2J value of 321 cm(-)(1) was interpreted as originated from isolated antiferromagnetically coupled dinuclear copper units. The EPR parameters are g(x)() = 2.07(1), g(y)() = 2.02(1), g(z)() = 2.33(1), D = 0.347(10) cm(-)(1), E = 0.0034(5) cm(-)(1). The dinuclear subunits are likely candidates for the catalytically active Cu species in copper(II)-catalyzed oxidation of carboxylic acids.

Lewatit R VP OC 1065 is a promising material for direct air capture of CO 2 . However, it was found that serious oxidative degradation already started from 80 °C. In this DFT study, oxidative degradation is described as a series of well-known reactions in air-oxidation chemistry. Oxidation of the resin starts with the formation of an α-benzyl amino hydroperoxide. Thermal decomposition of the α-benzyl amino hydroperoxide is the second step and leads eventually to the corresponding amide (R(CO)NH 2 ) and the half-aminal (RCH(OH)(NH 2 ). The half-aminal further solvolyzes predominantly to an aldehyde (RCHO). Both the amide and the aldehyde are responsible for the experimentally observed loss of CO 2 capacity as these groups are not able to capture CO 2 . The rate-determining step in oxidative degradation is usually the decomposition of the hydroperoxide, but in this case the formation of the α-benzyl amino hydroperoxide cannot be excluded. The apparent contradiction between the results of Hallenbeck et al. and Yu et al. with respect to the oxygen content before and after exposure of the resin to air at high temperature is explained by the difference in H 2 O content before and after and oxygen incorporation by amide and aldehyde formation after exposure to air. The loss of nitrogen content on exposure to air at high temperature is explained by the formation of aldehydes.

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