Kristallogrpahie & Geomaterialforschung

.

 

Crystalline Microporous Materials group – Current projects


Comparative, modelling-based investigations of pharmaceutical adsorption in zeolites


DFG Heisenberg Grant (project no. 455871835)

Zeolites are a class of crystalline inorganic materials consisting of a three-dimensional framework of corner-sharing tetrahedra. By virtue of their intrinsic porosity, zeolites find use in various large-scale applications, such as catalysis, ion exchange, and separation. Beyond these established uses, they could also be employed in applications involving the adsorption of pharmaceutically active compounds and related functional organic molecules, notably in the removal of emerging organic contaminants from wastewaters and in drug delivery. Within this project, atomistic modelling methods at different levels of theory (force field simulations, density functional theory) are used to study the interaction of zeolites with functional organic molecules, with most emphasis on pharmaceuticals and personal care products (PPCPs). Different types of zeolites will be considered in different parts of the project, including hydrophobic all-silica zeolites (see below), cation-exchanged zeolites, and natural zeolites (see below). On the one hand, these calculations have a predictive purpose, aiming to identify zeolite-guest combinations that could find use in applications. On the other hand, they will contribute to a better understanding of the interactions that govern the adsorption behaviour of relatively complex organic molecules.


Adsorption of pharmaceuticals and personal care products in hydrophobic zeolites


DFG Research Grant (project no. 492604837)

PhD student: MSc Jakob Brauer

In this project, a hierarchical, combined computational-experimental approach is used to study the adsorption of PPCPs of environmental relevance in hydrophobic all-silica zeolites. To start with, a screening of a large number of zeolite-PPCP combinations with force field simulations is performed to identify combinations of particular interest. These combinations are then studied in more detail using electronic structure calculations in the framework of density functional theory, looking at various aspects like dominant interactions and adsorption-induced deformations. The role of guest-guest interactions is also explored. The computational parts are complemented by experimental studies for a limited number of zeolite-PPCP combinations. These experiments, which will include both the measurement of liquid phase adsorption isotherms and the further characterisation of PPCP-loaded zeolite samples, will be carried out in collaboration with the group of Prof. Michael Wark (Technical Chemistry, Carl von Ossietzky University Oldenburg).


Optimising clinoptilolite adsorbents for the adsorption of pharmaceuticals and related compounds: A computational approach


Funded by the Central Research Development Fund of the University of Bremen

PhD student: MSc Lobna Saeed Abdelrazik Aly

Clinoptilolite is the most frequent natural zeolite, which can be mined in large quantities (albeit with limited purity) at relatively modest cost. Clinoptilolites have been found to be promising adsorbents for the removal of environmentally harmful PPCPs from wastewater. Due to their good biocompatibility, they could also find use as host material for drug delivery applications. In this project, the adsorption of PPCPs at the external surfaces of clinoptilolite crystals will be modelled using density functional theory (DFT) calculations. The first part of the project will focus on a construction of realistic surface models of natural and cation-exchanged clinoptilolites. The following two parts will investigate the adsorption of selected PPCPs at these surfaces using DFT structure optimisations and, for cases of particular interest, DFT-based molecular dynamics simulations. A comprehensive analysis of the interactions governing PPCP adsorption will provide a molecular-level understanding of the adsorption process. In addition, it will be evaluated how the strength of the zeolite-PPCP interaction can be “tuned” through cation exchange. These calculations will allow for a prediction of particularly suitable clinoptilolite-based adsorbents for applications in wastewater treatment or drug delivery, providing important input for future experimental studies.


Past projects


Beyond tetrahedral coordination in zeolite-type materials - A computational approach


DFG Research Grant (project no. 389577027), May 2018 to September 2021

The crystal structures of zeolites and related zeolite-like materials (zeotypes) consist of a three-dimensional framework of corner-sharing TO4 tetrahedra (where T = Si, Al, P…). While this implies that the T atoms have a coordination number (CN) of 4, there are instances where a coordination of additional ions or molecules results in an increase of the CN of some T atoms to 5 or 6 without affecting the tetrahedral connectivity of the framework. In this project, dispersion-corrected DFT calculations were employed to investigate the structures of zeolites and zeotypes with such “higher-coordinated” T sites, as well as the dynamic behaviour of the coordinated species and the framework as a whole. The two parts of the project focussed on the local environment of fluoride anions in all-silica zeolites and other neutral-framework systems on the one hand, and on the coordination of water molecules to framework aluminium atoms in aluminophosphate zeotypes on the other hand. Altogether, the calculations delivered unprecedented insights into the local structure and dynamic behaviour of complex porous solids, resulting in an in-depth understanding that would, in many cases, not be possible on the basis of experimental results alone.


Computational studies of host-guest interactions in zeolites


Funded by the Central Research Development Fund of the University of Bremen, February 2014 to May 2018

Atomistic simulations were employed to study the adsorption of different guest molecules in zeolites and zeotypes. Topics included the potential use of aluminophosphate-based zeotypes (AlPOs) for the separation of gas mixtures (e.g., CO2/N2 and CO2/CH4) and the interaction of water with AlPOs and silicoaluminophosphates (SAPOs), which could find use as adsorbents in thermal energy storage. Another focus of the project lay on the benchmarking of DFT calculations against experimental crystal structures and, where available, thermochemistry data.



Updated on 08.11.2022 by Chr.Vogt/MiFi, FB 05, Universität Bremen