Metal-Organic Frameworks (MOFs)
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Metal-Organic Frameworks (MOFs) are functional materials that have applications in catalysis, drug delivery and water purification. MOFs are polymers formed by coordination between metal ions with polydentate organic linkers, producing extended three-dimensional structures with a porous network that can trap adsorbates. The extent and the availability of the porous network of the MOFs are responsible for their efficacy in devices or sensors. Anomalies within the device that restrict the size and availability of pores would render it inefficient. These may arise due to (a) the formation of defects where the linkage between the “metal” and the “organic framework” is disrupted, leading to faulty propagation of the crystal structure over the base template, or (b) coordination of the adsorbed solvent/impurities to the metal centers. Characterization techniques like electron microscopy, atomic force microscopy (AFM), and X-ray diffraction studies can measure the morphology and crystalline defects in MOFs but are generally insensitive to adsorbates or their chemical identity in MOF pores. Most importantly, structural understanding does not offer insight into the chemistry of MOFs, which is at the heart of their utility.
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J. Phys. Chem. Lett., 2017, 8(21), pp 5325-5330. DOI: 10.1021/acs.jpclett.7b02104
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Techniques like optical microscopy cannot answer these questions either, but when coupled to infrared, IR imaging lets us see into the chemistry of MOF pores! Currently, there exists no standard technique that can address these issues and unequivocally ascertain spatial homogeneity, or lack thereof, in MOFs in regard to their sorption properties. Hence, there is an unmet need to examine the MOF structure and sorption chemistry to complement the structural and morphological information on traditional characterization techniques
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