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Porous Metal-Organic Frameworks for Energy Storage Applications: Design, Synthesis and Mechanism Studies
Abstract
The self-assembly of metal ions and organic linkers could afford 3-dimensional
(3D) porous metal-organic frameworks (MOFs). They are promising materials for clean
energy applications including carbon capture, hydrogen storage and methane storage.
The primary goal of this research is the synthesis and characterization of new MOFs for
these applications, and their structure-property relationship studies based on both
experiments and simulations.
Firstly, a stable magnesium MOF with 1-dimensional (1D) channel structure was
synthesized. In-situ powder X-ray diffraction studies reveal its interesting phase
transitions properties. After removing coordinated solvent at magnesium chains, this
MOF can selectively adsorb CO_(2) over N_(2).
Secondly, by varying the conditions in the solvothermal reaction, five MOFs with
diverse structures were synthesized from a tetratopic ligand. Hydrogen storage properties
were studied for these MOFs. A list of factors including catenation, metal nodes, charge,
topology and pore size are evaluated for hydrogen storage application.
In addition, four isostructural MOFs with various functionalized pore surfaces
were synthesized from a series of di-isophthalate ligands. These MOFs exhibit a new
network-topology and very high hydrogen uptake. They also showed reasonable
adsorption selectivity of CO_(2) over CH_(4) and N_(2).
Finally, high pressure methane uptake properties have been studied both
experimentally and computationally for the series of isostructural MOFs with varying
functional groups. All showed very high methane storage capacity at 298 K, 65 bar.
Structure-property relationships were established for these MOFs, and simulations were
employed to understand the mechanism of methane storage in MOFs. The role of copper
paddlewheels and other adsorption sites for methane was evaluated. By thorough studies
and careful analyses of simulation and experimental data, we proposed three novel
mechanisms for methane storage in MOFs. Significantly, with the help of the mechanism
studies, another two MOFs were designed, synthesized and discovered to have even
higher methane storage capacities.
Ligand design has been a powerful tool in synthesizing new MOFs. Besides
surface area, pore size has been discovered to be a key factor for gas storage capacities of
MOFs. These findings could serve as guidance for rational design of better performing
materials for clean energy applications.
Citation
Liu, Yangyang (2014). Porous Metal-Organic Frameworks for Energy Storage Applications: Design, Synthesis and Mechanism Studies. Doctoral dissertation, Texas A & M University. Available electronically from https : / /hdl .handle .net /1969 .1 /152750.