The samples of MOF-303 and CALF-20 were the exact same samples as used in previous work, and the synthesis details have already been reported. Briefly, to synthesize CALF-20, zinc oxalate, 1,2,4-triazole, and methanol were added to a 125 mL Teflon autoclave housed in a convection oven. The autoclave was heated to 180 °C and held isothermally for 48 hrs. The resulting product was washed with methanol and air-dried until only a white powder remained.