A Simple Method for Teaching Bragg?s Law in an Undergraduate Teaching Laboratory with the Use of Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are a class of porous materials that are often crystalline with high surface area and structural tunability. In this laboratory experiment designed for inorganic chemistry students at the undergraduate level, students complete a two-step experiment where they will first (i) synthesize two isostructural zirconium-based MOFs, UiO-66 and UiO-67, and then (ii) isolate and characterize the materials using powder X-ray diffraction (PXRD). A simple solvothermal procedure was developed for the synthesis of UiO-66 and UiO-67 using the air/moisture-stable zirconyl chloride octahydrate as a starting reagent. Depending on the equipment available, the MOFs can be further characterized by nitrogen adsorption analysis for surface area determination using Brunauer-Emmett-Teller (BET) theory, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), thermogravimetric analysis (TGA), 1H nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy (SEM). Upon synthesizing the MOFs and collecting the characterization data, students analyze and describe their results by answering a series of questions included in the laboratory manual. This exercise will allow students to develop practical laboratory skills while expanding their knowledge on some fundamental concepts in inorganic chemistry, materials chemistry, MOFs, crystallography, and other characterization techniques as availability allows.