Tuning Metal-Organic Frameworks and Porous Polymers for Gas Storage and Separations

The focus of this research is to investigate how the exact shape, functionalization, and pore structure, specifically the distribution and filling of meso- and micropores, affects the chemical environment within the pores, especially when it comes to the adsorption and condensation of gas molecules. This is accomplished through pore engineering, tuning the nanostructures of the material for a particular application. However, the true rational design of MOFs and other porous materials is still a goal we have taken only a few small steps towards. Thus, considerable effort has also been devoted to the development of synthetic techniques necessary to grow new kinds of MOFs and PPNs in a planned manner. The development of an extensive library of synthetic and post-synthetic modification techniques for MOFs and porous polymers is how researchers will be able to eventually achieve ‘total synthesis’ of desired porous materials, rather than relying on trial and error and serendipitously discovered existing materials. Organic chemists were able to achieve the total synthesis of complex natural products only after centuries of synthetic and theoretical study. Porous materials chemists will eventually be able to design or mimic complex pore environments such as enzyme active sites or catalysts for complex tandem and multistep reactions. However, this will only occur if we can develop a similarly massive library of complicated synthetic techniques and improved theoretical understanding of crystallization processes. Our work towards this goal begins with a comprehensive review of recent developments in MOF synthesis, especially the development of new synthetic methods to impart intricate functionality into ultrastable MOFs. Our group’s development of Kinetically Tuned Dimensional Augmentation, Post-synthetic Metathesis and Oxidation, and Sequential Linker Installation and Cluster Metalation have contributed to the grand challenge of the rational design and total synthesis of MOF structures and greater control of pore environments. As a related subject, we also cover recent development in the design of various types of porous carbons for hydrogen storage. We then cover the development of pre-synthetic modulation methods to alter MOF properties and produce new MOFs. Using lithium salts as a modulator, the porosity and hydrogen uptake of anionic MOFs can be improved. We can also use Mn sources in different oxidation states to produce Mn(II) MOFs with different structures and porosities with the same linker. Post-synthetic modification techniques are explored through the loading of sorbents for CO2 and methane uptake with liquid alkylamines and alkanes, respectively, in order to combine adsorption and absorption in a single material and efficiently use an available volume. Both techniques demonstrate improvements in uptake over the unmodified materials, with a focus on their exceptional stability, cyclability, and cost-effectiveness, as they are targeted for widespread application