Nanoporous metal-organic frameworks (MOFs) have attracted tremendous interest due to their potential applications in gas-storage, gas separation, gas sensing, and catalysis. MOFs consist of metal-oxygen polyhedera interconnected with a variety of organic linker molecules, resulting in tailored nanoporous materials. With a judicious choice of organic linker groups, it is possible to fine-tune size, shape, and chemical functionality of the cavities and the internal surfaces. This unique structural feature offers unprecedented opportunities in small-molecule separations as well as chiral separations and catalysis. Prototypical iso-reticular metal-organic frameworks (IRMOFs) have been extensively studied among MOFs due to the simplicity of their synthesis and the variety of their potential applications. IRMOFs are a specific series of metal-organic frameworks developed by Yaghi and his coworkers. All IRMOFs are composed of oxygen-centered Zn4O tetrahedra interconnected with dicarboxylate linkers, forming a cubic type three dimensional (3D) porous network with high surface area. Despite a great deal of research in the synthesis and characterization of MOFs, there have been relatively few reports on the development of their applications, such as the fabrication of MOF thin films and membranes for gas separations. This is mainly due to the challenges associated with relatively difficult heterogeneous nucleation (seeding) and growth of MOFs on supports, and crack formation compared to their counterparts. Thin films and membranes of MOFs have great potentials for applications in membranebased gas separations, reactors, chemical sensors, and nonlinear optical devices. In this dissertation, the fabrication of IRMOF-1 membrane using a novel seeding method and its gas diffusion properties has been demonstrated. Introduction of the new seeding method for MOFs using microwaves resulted in well inter-grown IRMOF membranes showing Knudsen type transport of small gases through its pore. The heteroepitaxial growth of one IRMOF on another produced multi-layered IRMOF membranes. In addition, postsynthetic modification (PSM) of IRMOFs created functionalized membranes with enhanced stability against water as well as reduced crack formation during membrane fabrication. Lastly, hierarchical IRMOFs with improved CO2 adsorption properties were synthesized via PSM with cyanuric chloride.

Made available in DSpace on 2014-06-12T23:15:25Z (GMT). No. of bitstreams: 2 arquivo9224_1.pdf: 3464173 bytes, checksum: 94687aaa129bb4d86a43fd62041c9969 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2007 / O gás natural é principalmente armazenado em cilindros por sua compressão em altas pressões (205 atm). Esta pressão pode ser significativamente diminuída pelo armazenamento deste gás num material sólido poroso devido à interação entre os átomos do material e do gás (fenômeno da adsorção), o que diminui os custos e riscos do processo. Um exemplo de uma classe de materiais que podem ser usados para esse fim são as rede metal-orgânica isorreticular (IRMOF), cuja forma cristalina altamente porosa de rede cúbica é constituída por vértices metálicos conectados por espaçadores orgânicos aromáticos. Realizamos cálculos ab initio/semi-empíricos e de simulações de Dinâmica Molecular do material IRMOF para compreender detalhes da sua interação com componentes do gás natural, com ênfase no efeito da concentração do gás na sua difusão no material, na determinação dos sítios de ligação do material com o gás e na influência do tamanho e ramificação dos hidrocarbonetos. Percebemos a ocorrência de transição de fase gás-líquido do metano dentro da IRMOF em altas concentrações. Realizamos, então, simulações computacionais de Monte Carlo grã-canônico para obter isotermas de adsorção do material IRMOF com o metano. Com isso, sugerimos um novo material tipo IRMOF com potencial de maior eficiência no armazenamento de gás natural que os até então sintetizados e propostos na literatura. Este trabalho exemplifica como a química computacional pode atuar economizando tempo e esforço de procedimentos experimentais no desenvolvimento da tecnologia de gás natural