CAREER: Zwitterionic Metal-Organic Frameworks with Multi-Stimulus-Responsive Properties

Non-technical Abstract: This CAREER project is an integrated research, education, and outreach program funded by the Solid-State and Materials Chemistry program of the Division of Materials Research. The overall goal of the research plan is to devise strategies that enable the synthesis of a new class of advanced porous materials composed of charge-separated molecular building blocks. These charges can perform a desired function to attract specific guest molecules within the material's pores. In one line of research, the ability of light to interact with these charges will be explored to trigger the release of guest molecules to determine if the material can be regenerated to its original state. This feature would be particularly useful for a multitude of environmental applications that seek the adsorption or separation of gases, such as hydrogen storage and carbon capture respectively with the general objective to counteract global warming. Leveraging the research activities is the educational plan that will allow Clarkson University to offer a stronger, ACS-approved chemistry program, the foundation for a broad, rigorous chemistry education that provides students with the intellectual, experimental, and communication skills to become effective professionals. The outreach program is hands-on and incorporates state-of-the-art crystallography instrumentation to significantly strengthen and expand the high school to college pipeline for students from the rural North Country of New York State by increasing their exposure to and interest in STEM fields and careers. An X-ray diffraction workshop will provide participants with the training to understand and appropriately utilize the most precise method of determining crystal structures, thus allowing the analysis of fundamental structure-property relationship. Technical Abstract: The proposed research plan addresses fundamental questions essential to the advancement of functional porous materials with multi-stimulus-responsive adsorption properties and rapid controllable release of guest molecules. Proposed is the use of zwitterionic metal-organic framework (ZW MOF) building blocks whose molecular surfaces show well-separated intramolecular charges with tunable electric field gradients. These gradients present potential multi-point adsorption sites that can be designed at a molecular level within the zwitterionic ligands prior to MOF self-assembly. Once zwitterions are incorporated into MOFs, their electric field gradients yield charged organic surfaces (COSs) within the pores, which in turn polarize guest molecules, resulting in defined adsorption properties. The most important feature of zwitterions is their sensitivity to external stimuli (e.g. light or electrochemical), resulting in switchable COSs that enable significant control and tunability of adsorption properties. Specific approaches are to: (1) Design and investigate ZW ligands as a new, simple, and controllable means to introduce COSs into pore linings to create MOFs with defined host-guest interactions; (2) Explore post-synthetic modification reactions as alternative routes for introducing ZW functionalities into MOFs; and (3) Demonstrate and optimize the multi-stimulus-responsive tunability of COSs by controllable release of guest molecules from MOF pores. These experiments will ultimately provide a powerful tool to tailor MOFs with tunable host-guest interactions and will generate fundamental knowledge on a novel type of multi-stimulus-responsive material with distinct adsorption and desorption properties. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.