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
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.
Adsorption of pharmaceuticals and related compounds in cation-exchanged zeolites – A computational perspective
PhD student: Sujon Kumar Mitro
In
this project, atomistic simulations in the framework of
dispersion-corrected density functional theory (DFT) are used
to study the interaction of pharmaceuticals and related
compounds with zeolite adsorbents containing different
cations. The first part of the project comprises a thorough
validation of the DFT methodology. In the second part, the
interaction between cationic zeolites and a set of “model
compounds”, relatively simple pharmaceuticals containing
representative functional groups, is studied systematically,
considering different cation species as well as variations in
Si/Al ratio and zeolite framework type. A set of case studies
is performed in the third part: On the basis of published
experimental studies, organic species of particular interest
in the context of wastewater treatment or drug delivery are
identified. DFT calculations are then employed to study their
interaction with cationic zeolites. These calculations will
consider various additional aspect that are relevant for
real-world applications, such as the impact of temperature and
the competitive adsorption of water.
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.