Ion exchange 100 mg of the as-synthesized SU-MOF was ion-exchanged by stirring the MOF in 6 mL 1M NaCl or KCl solution for 24 hours at room temperature. For the more hydrophobic MOFs synthesized with trialkylamines, ion exchange was also performed at 80 °C. The ionexchanged MOF was separated by centrifugation at 3800 rpm for 10 minutes and the process was repeated a second time. After washing, the ion-exchanged MOF was dried in an oven at 70 °C overnight (Supplementary Fig. ).