Magnetic Tunability in RE-DOBDC MOFs via NO Acid Gas Adsorption

The magnetic susceptibility of NO-loaded RE-DOBDC (rare earth (RE): Y, Eu, Tb, Yb; DOBDC: 2,5-dihydroxyterephthalic acid) metal-organic frameworks (MOFs) is unique to the MOF metal center. RE-DOBDC samples were synthesized, activated, and subsequently exposed to humid NO. Each NO-loaded MOF was characterized by powder X-ray diffraction, and the magnetic characteristics were probed by using a VersaLab vibrating sample magnetometer (VSM). Lanthanide-containing RE-DOBDC (Eu, Tb, Yb) are paramagnetic with a reduction in paramagnetism upon adsorption of NO. Y-DOBDC has a diamagnetic moment with a slight reduction upon adsorption of NO. The magnetic susceptibility of the MOF is determined by the magnetism imparted by the framework metal center. The electronic population of orbitals contributes to determining the extent of magnetism and change with NO (electron acceptor) adsorption. Eu-DOBDC results in the largest mass magnetization change upon adsorption of NO due to more available unpaired f electrons. Experimental changes in magnetic moment were supported by density functional theory (DFT) simulations of NO adsorbed in lanthanide Eu-DOBDC and transition metal Y-DOBDC MOFs.