Desorption Of Small Molecules Research Articles

Microporous Organic Polyimides for CO2 and H2O Capture and Separation from CH4 and N2 Mixtures: Interplay between Porosity and Chemical Function

Porous polyimides have been considered to be a promising material class for gas capture and sequestration, leading to the synthesis of a substantial number of individual networks with noteworthy sorption properties. In spite of these efforts, the vision of a chemical control of adsorption and desorption of small molecules, in particular, for the competing uptake of technical relevant gas mixtures, is still hardly investigated. Here, we present a systematic study of five new polyimide networks based on a set of linkers with chemical functionalities covering the full range from hydrophobic to hydrophilic interactions. The corresponding microporous organic polyimides (MOPI-I to -V) were synthesized successfully based on a condensation reaction between amino and anhydride linker molecules in m-cresol at high temperatures, resulting in cross-linking degrees beyond 95% in all cases. Argon and carbon dioxide isotherms reveal surface areas up to 940 m2/g with ultramicroporosity, about 50% microporosity and high t...

Effect of Calcium Ion Concentration on Small Molecule Desorption from Alginate Beads

Spherical alginate beads were prepared by ionotropic gelation of sodium alginate through the use of calcium ions. Pyranine (Py) was added to the alginate solution as a small molecule probe for fluorescence studies. Desorption of Py in water from the alginate beads cross-linked with calcium ions was studied by using the steady state fluorescence technique. The fluorescence emission intensity (I) from Py was monitored during the desorption process at 512 nm using the time drive mode of the spectrofluorometer. The increase in I was attributed to Py release from the beads. The Fickian diffusion model was used to calculate the desorption coefficients, D, which were found to be increased up to 3% (w/v) CaCl2 concentration in the beads, and then decreased with a further increase of CaCl2 content. On the other hand, the encapsulation efficiency of Py in the calcium alginate beads presented the reverse behavior compared to D. It was observed that, when the content of CaCl2 was increased, the incubation time, t0, for the start of desorption increased.

Laser‐induced desorption of small molecules from oxide surfaces: A first‐principles study

AbstractRecent efforts in the theoretical simulation of laser‐induced desorption of small molecules from surfaces are summarized. As a representative example, photodesorption of CO molecules from a Cr2O3(0001) surface is investigated since detailed quantum state resolved experimental results are available for this system.In particular, vectorial properties such as the alignment of the desorbing species are considered. Furthermore, the influence of surface temperature as a control parameter is investigated, and lateral velocity distributions are calculated and compared with experimental results.All simulations presented in the present study are based on ab initio potential energy surfaces (PESs) for the electronic ground state as well as electronically excited states involved in the desorption process. These PESs provide the prerequisite for extensive high‐dimensional quantum mechanical simulations of the dynamics of nuclear motion based on a stochastic wave packet scheme.These wave packet calculations allow for a detailed microscopic understanding of experimental results and provide a perspective for future experiments.