Linker Design Principles and Implementation in High Performance Microporous Coordination Polymers.

[摘要] Due to their tunable and varied structures, microporous coordination polymers (MCPs) are considered promising candidates for gas storage, separations, and catalysis. Performance in these applications is highly dependent on surface area, which is greatly impacted by factors such as incomplete guest removal, framework collapse, non-optimal linker or metal cluster geometry, and/or framework interpenetration. The studies within this thesis serve to address these problems by offering a method for understanding surface area as well as the implementation of novel linker design strategies for avoiding common structural impediments to achieving high surface area materials.A surface area prediction method is introduced for the rational dissection of structures into building block components so that surface area contributions from linker and metal cluster units may be recognized. MOF-5 and HKUST-1 are used as prototypical structures to analyze MCPs with octahedral M4O(CO2R)6 and paddlewheel M2(CO2R)4 metal clusters. It was determined that the theoretical upper limit of a benzene linked system is approximately 10,500 m2/g and that features such as ring fusion, functional group substitution, and interpenetration reduce MCP surface areas.Implementation of design guidelines determined through theoretical studies led to the development and application of two synthetic strategies. In one method, a large linker containing seven benzene units is stabilized with six carboxylate groups to form a non-interpenetrated MCP, UMCM-300. The lack of interpenetration is an outstanding feature that is attributed to the formation of a (3,24)-connected network that contains cuboctahedral cages containing small pore apertures too small to allow interpenetration.In the second method, five examples of non-interpenetrated MCPs are derived by employing linkers with symmetry inequivalent coordinating groups. Gas sorption in polymorphic frameworks, UMCM-152 and UMCM-153, reveals nearly identical properties with BET surface areas in the range of 3300-3500 m2/g and excess hydrogen uptakes of 5.7 and 5.8 wt % at 77 K. In contrast, adsorption of organosulfur compounds shows remarkably different capacities demonstrating the importance of pore size and shape on liquid phase adsorption. MCPs constructed by this method also exhibit rare metal clusters and network topologies previously unseen, demonstrating the potential for reduced symmetry linkers in forming MCPs with new properties.

[发布机构] University of Michigan

[效力级别] Chemistry

[关键词] Microporous Coordination Polymer;Chemistry;Science;Chemistry