Περίληψη σε άλλη γλώσσα
In the present PhD thesis we have studied the hydrogen storage performance of
IsoReticular Metal-Organic Frameworks (IRMOF) and Covalent-Organic
Frameworks (COF), using various theoretical methods and computational techniques.
IRMOF and COF materials have been proposed as hydrogen storage materials from
the first time that they were synthesized, due to their unique physicochemical and
structural properties.
Firstly we studied IRMOF materials for hydrogen storage. Preliminary results had
shown that hydrogen was interacting with these materials by weak van der Waals
interactions. It was proposed that the enhancement of the interaction strength would
lead to a better hydrogen storage performance of these materials. One way to do that
is the introduction of point charges into the material, which can be done by decorating
the pore with Li atoms. Li atoms can be incorporated either by interacting with the
aromatic systems of the structures or by the formation of –SO3Li and –OLi g ...
In the present PhD thesis we have studied the hydrogen storage performance of
IsoReticular Metal-Organic Frameworks (IRMOF) and Covalent-Organic
Frameworks (COF), using various theoretical methods and computational techniques.
IRMOF and COF materials have been proposed as hydrogen storage materials from
the first time that they were synthesized, due to their unique physicochemical and
structural properties.
Firstly we studied IRMOF materials for hydrogen storage. Preliminary results had
shown that hydrogen was interacting with these materials by weak van der Waals
interactions. It was proposed that the enhancement of the interaction strength would
lead to a better hydrogen storage performance of these materials. One way to do that
is the introduction of point charges into the material, which can be done by decorating
the pore with Li atoms. Li atoms can be incorporated either by interacting with the
aromatic systems of the structures or by the formation of –SO3Li and –OLi groups.
We have studied the last two cases by using first principles computational methods
and we have found that the interaction strength was enhanced in the modified IRMOF
materials by a factor of three. Further investigation by performing GCMC simulations
showed that there was also an enhancement of the total hydrogen storage abilities of
these materials both at cryogenic and room temperature.
Next we have evaluated the hydrogen storage abilities of the COF family of
materials. We were focused on 3-dimensional COF materials (3D-COF), since these
material had superior physicochemical characteristics than other COF that made them
more promising for hydrogen storage. We have performed first principles calculations on these materials to study the interaction of hydrogen with the individual building
blocks that these materials were made from. We found that hydrogen interacted with
the material by weak van der Waals and dispersion forces, where the strength of these
interactions was similar to those of IRMOF. GCMC simulations showed that these
materials had exceptional hydrogen storage capacities, which can be explained by the
low density of these materials and the high surface and the pore volume that they
preserve. The best of these materials was COF-105, which reach 20 %wt at 77K and
100bar, which was by far the best performed known material in the field. In order to
increase the hydrogen storage ability of these materials, we have introduced –OLi
groups in the structure of the best performed COF-105. We found an enhancement in
both the interactions of the hydrogen with the material and of the total hydrogen
amount that could be stored in these materials. Finally, we have designed new 3DCOF
materials based on ctn network and by using the connectivity of COF-102.
These new COF were firstly optimized by molecular mechanics method with the use
of an appropriate modified MM3 forcefield and then their storage abilities were
investigated by GCMC simulations. We found that the best of the materials that we
designed could exhibit 27 %wt at 77K and 100bar, well above the best performed
COF-105.
περισσότερα