The sequestration of atmospheric CO2 is one of the most pressing challenges of our time. MOFs have demonstrated extraordinarily high gas capture capacities -the highest, in fact, among all known adsorbents. In this experiment, students directly assess the effectiveness of their MOFs for CO2 uptake under ambient conditions. Figure illustrates the steps of the procedure. First, a plastic bottle is filled with dry ice. As the dry ice sublimes, gaseous CO2 displaces the air in the bottle. A balloon is then placed over the plastic bottle and allowed to fill with CO2 gas generated by the dry ice. The CO2-filled balloon is then placed tightly over an empty vessel and allowed to remain in place for approximately 15 minutes. This ensures that most of the air present in the vessel is displaced with CO2 gas as it is more dense than air. The balloon is then removed, and the MOF is quickly added to the vial which is then capped and re-weighed. After the initial mass of MOF before adsorption is recorded, the balloon is again secured to the vessel and left for 30 minutes to allow the MOF to adsorb the CO2 gas. After 30 minutes, the balloon is removed and the vessel is recapped and An example of representative CO2 adsorption data is shown in Tables and. Students use the ideal gas law to quantify the amount of CO2 adsorbed (see the example calculation given in the Supporting Information). HKUST-1 and AlF adsorb approximately 1.0 and 0.7 mmol CO2/g MOF, respectively. These values are in agreement with the expectation that HKUST-1 should have higher CO2 uptake than AlF. In these CO2 adsorption experiments, it is important to recognize that the capacity for the MOFs to adsorb CO2 is due not only to pore size, surface area, and volume, but also to experimental factors such as temperature and humidity. Finally, we note that sand or table salt can be used as non-porous controls; they do not adsorb measurable amounts of CO2 when used in place of a MOF in an otherwise identical experiment.