Fig. 1. Typical NMR-active nuclei found in MOFs like MIL-53 (ref. 6) and their modifications. NH₂-functionalized linkers are depicted as used in MIL-53-NH₂(as).⁷ This topology was also prepared as a mixed-metal compound MIL-53(Al/Ga),⁸ see below. In situ NMR can detect adsorbed molecules like ¹³CO₂ and their interactions with the MOF.