With nearly 8 billion people in the world, access to clean water is of paramount importance and water pollution is a global threat. Dyes, which are ubiquitous in nearly every manufacturing industry (e.g. paper, plastics, textiles, food, medication, etc.) have become a significant class of water pollutants. Many dyes undergo chemical changes in wastewater and are not easily degradable. These chemical transformations yield compounds that are harmful, significantly contributing to poor water quality that often proves fatal for aquatic life due to depleted oxygen availability. One solution to this problem is to remove the chemical pollutants by adsorption. MOFs are excellent candidates for dye adsorption given their high accessible internal surface areas. In this set of experiments, students monitor the concentration of a solution of methylene blue or Lugol's solution, an aqueous solution prepared from water, I2, and KI, as the solute adsorbs to the MOF powder. The previously published work of Kuntzleman et al. describes a method by which a smartphone app can be used to teach Beer's Law and explore concepts and equations involved in absorption spectrometry. Taking inspiration from this work, we used this smart phone app to determine the color intensity of a solution as dye is adsorbed on to a MOF, allowing quantification of the amount of dye adsorbed. We note also a recent report in which the MOFs MOF-5, ZIF-8, and MIL-101(Fe) were used to adsorb I2 from methanol. The first step in the dye adsorption experiments requires setting up an apparatus for using a smart phone colorimeter app as shown in Figure . Detailed descriptions are provided in the Supporting Information. The measurement apparatus is a modified version of that described previously. A hole just large enough to fit the vial containing the dye solution is cut into the top surface of a cardboard box. A second, smaller hole is cut into one of the sides of the box to accommodate visualization with a smart phone camera. The opposite side of the box is cut away completely and is replaced with a piece of colored stock paper. Once the measurement apparatus is constructed, it can be stored and used indefinitely.