18.06.2020 Hot article in Physical Chemistry Chemical Physics

A recently published paper has been selected as PCCP hot article 2020.

A recent paper in Physical Chemistry Chemical Physics (a journal published by The Royal Society of Chemistry) has been selected by the journal editors as 2020 HOT PCCP article. The paper reports about research on key transport properties of ordered mesoporous silicas, which are resolved by comprehensive methodology. Compared with the extensive literature on zeolites, data about hindered diffusion in ordered mesoporous silicas remain scarce and quantitative hindrance factor expressions, which quantify the extent to which diffusion of finite-size solutes through a material is hindered compared with free diffusion in the bulk liquid, are entirely lacking. Ideally, this information is provided together with an explanation of how the relevant morphological properties of a material shape the actual hindrance factor expression.

Reconstructions of ordered SBA and KIT materials for simulations of hindered diffusion.
Figure: Janika Hochstraßer

In that article, morphology–transport relationships were studied through direct (pore-scale) numerical simulation of hindered diffusion in realistic geometrical models of the pore space obtained from physical reconstruction by electron tomography. Accessible porosity and effective diffusion coefficients resulting from steric and hydrodynamic interactions between solutes and pore space confinement were monitored as a function of the ratio between solute size and mesopore diameter. The derived hindrance factor expressions of the materials are their signature, reflecting individual morphological features as the consequence of their preparation history. The elaborate reconstruction–simulation approach required to establish this knowledge is justified considering that the detailed information provided can become the decisive factor to boost the performance of a process that depends on efficient and selective solute transport. This applies to the immobilization of bulky species (nanoparticles, enzymes, polyhedra, clusters) on the internal surface of a material, to heterogeneous catalysis and liquid chromatography utilizing spatial confinement effects for size-selective transport, reaction, and separation, as well as to the controlled release of drugs from the pore space. In each case, the effects of hindered diffusion and associated time-scales, decoupled from complex interfacial effects (e.g., adsorption and reaction), have to be quantitatively known.

Link to the article:

J. Hochstrasser, A. Svidrytski, A. Höltzel, T. Priamushko, F. Kleitz, W. Wang, C. Kübel, U. Tallarek, Morphology–transport relationships for SBA-15 and KIT-6 ordered mesoporous silicas. Phys. Chem. Chem. Phys. 2020, 22, 11314–11326.