The internal standard stock solution was prepared by dissolving MA (75.23 mg, 0.648 mmol) in D2O (8149.9 mg, 406.933 mmol). Since this MOF (MAF-6) is digested using D2SO4 (for qNMR purposes), we prepared the calibration curve by addition of a representative amount of D2SO4. The weighed mass of each compound can be found in Table . This reveals that, when using a relaxation delay of 30 s, there might be a slight (<0.1 %) underestimation of the concentration when using the signal of the aromatic protons. However, in the calibration curve, this was not observed.