Boosting the proton conduction in a magnetic dysprosium-organic framework by introducing conjugate NH4+-NH3 pairs

Metal-organic frameworks (MOFs) with inherent porosity and suspended acidic groups are promising proton conducting materials in water or aqua-ammonia media. Herein we report a new lanthanide phosphonate, namely, Dy 2 (amp 2 H 2 ) 2 (mal)(H 2 O) 2 center dot 5H 2 O ( MDAF-6 ). It possesses a 3D open-framework structure, and shows a high NH 3 adsorption capacity of 142.4 cm 3 /g at P / P 0 = 0.98 at 298 K due to acid-base interaction. Interestingly, the proton conductivity of MDAF-6-NH 3 is enhanced by five orders of magnitude compared to MDAF-6 after 8.5 h exposure in saturated NH 3 -H 2 O vapor, indicating the importance of coexistent conjugate acid-base pairs of H 3 O + -H 2 O and NH 4 + -NH 3 in promoting proton conduction. Magnetic studies of MDAF-6 revealed slow magnetization relaxation under zero dc field, characteristic of singlemolecule magnet behavior. This work provides not only a new multifunctional MOF material, but also a new strategy to improve proton conduction in aqua-ammonia medium. (c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.