Structures, thermal stabilities, and magnetic properties of four new lanthanide coordinative frameworks incorporating mixed organic ligands

In this study, we synthesized four new lanthanide coordination polymers: CKMOF-1 [Ce2(CO3)2(C2O4)(H2O)2] · 2H2O, CKMOF-2 [Ln2(C4H4O4)2(C2O4)(H2O)4] · 4H2O (Ln = Ce, Nd), and CKMOF-3 [Na2Nd2(C4H4O4)(C2O4)3] · 4H2O. For CKMOF-1, the cerium ions are extended with carbonate ligands to form networks possessing 2D inorganic skeletons, which are pillared by oxalate ligands to yield open channels featuring water molecules distributed within. For CKMOF-2, succinate ligands replace the carbonate ligands in the networks and separate 2D inorganic skeleton into 1D inorganic chains. Similarly, oxalate ligands act as pillars to generate an open framework with channels existing along multiple directions. For CKMOF-3, dimeric neodymium units are assembled with in-planar oxalate ligands to form honeycomb-like networks, which are pillared by out-of-plane oxalate ligands to generate an open framework with sodium counteractions distributed around the channel walls. The dehydrated solid [Ce2(CO3)2(C2O4)(H2O)2] retained the crystallinity of its original CKMOF-1 phase. The dehydrated solid [Nd(C4H4O4)2(C2O4)] maintained the framework porosity of CKMOF-2, but lacked long-range ordering; a reversible hydration process converted this distorted phase back to the highly crystalline state in CKMOF-2. Decreases in the values of χMT with decreasing temperature indicate that the main contributions from spin–orbital couplings were accompanied by weak magnetic interactions.