Probing Metal-Organic Framework Stoichiometry Using Quantitative NMR and TGA

Metal-organic frameworks are crystalline materials that do not always have a perfect stoichiometry, due to the presence of defects, modulators or mixed linkers. A common approach to quantify these defects is to define a value for ‘missing linkers’, typically done by thermogravimetric analysis (TGA). We propose the use of the (metal oxide) residue of TGA to quantify the metal content in combination with quantitative NMR spectroscopy of a digested sample for linker quantification. We demonstrate this simple concept for three examples, MAF-6, ZIF-8 and MOF-5.