Activation of Molecules in Confined Spaces:  An Approach to Zeolite−Guest Supramolecular Systems

Abstract

Ab initio calculations showing frontier molecular orbital energy modifications of a guest molecule when located inside a microporous zeolitic cavity are presented. Micropores of zeolites Beta, ZSM-12, and ZSM-5 have been modeled using all silica clusters from which it is found that the highest occupied molecular orbital (HOMO) energy of toluene increases when going from the gas phase state to restricted microporous environments. The influence of the zeolite cavity size and its chemical composition on the toluene HOMO energy are discussed. Regarding the size of the confining environment, it is found that the smaller the zeolite cavity the higher is the rise in toluene HOMO energy. The effect of the chemical composition on the toluene HOMO energy was tested in the ZSM-5 zeolite by varying the Al content. The results obtained showed that the frontier orbital energy increases upon decreasing the Al content of the cluster. As a consequence of the confinement effect, toluene reactivity in zeolite catalyzed reactions is expected to change toward a more covalent behavior in which electronic transference from the toluene molecule to an electronic acceptor will be more favored than in gas phase reactions.

Fab MOR03268 Triggers Absorption Shift of a Diagnostic Dye via Packaging in a Solvent-shielded Fab Dimer Interface

“…The highest occupied MO has been predicted to be more sensitive than the lowest unoccupied MO. 18,19 In order to test whether this theory can explain the observed redshift, we introduced a central cyclohexane ring into TSC to fill the protein cavity more completely. Indeed, MOR03268 shifted the absorption peak of the resulting Ch-TSC by 38 nm, compared to 32 nm observed with TSC.…”

Optimizing the performance of the entropic splitter for particle separation

“…A separation dependent on particles' mass and size is usually carried out a) New address: Institut für Theoretische Physik, Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany; Electronic mail: thomas.motz@uni-ulm.de by centrifugation 6 , whereas electrophoresis combines diffusion through a gel with an external electric field to sort out particles of different sizes and charges [7][8][9] . A purely size-dependent separation in its simplest form is realized by a sieve or porous materials 10,11 . The current techniques proposed for particle separation rely on forcing the particles to move at different velocities but in the same direction.…”

The adsorption of saturated and unsaturated hydrocarbons on nanostructured zeolites (H-MOR and H-FAU): An ONIOM study

“…The understanding and rational utilization of confinement effects will undoubtedly contribute to increasing the productivity, and selectivity of such chemical transformations [8][9][10][11]. Recently, experimental investigations in molecular details of structures and adsorption dynamics and interaction energies of hydrocarbons in zeolites have been reported [12][13][14][15][16][17][18].…”