Coordination polymers are structures based on metal ligand coordination strongly related to the same types found in MOFs. While MOFs are mainly three-dimensional networks, coordination polymers are one-dimensional strands or two-dimensional networks, that are held together by weak interactions such as van-der-Waals forces or hydrogen bonds in the solid state.
Opposed to transition metals, for which coordination numbers of 4 and 6 predominantly occur, rare earth metal centers have a higher coordinative demand, resulting in coordination numbers from 6 to 12. In the case of holmium, our workgroup was capable of synthesizing a one dimensional holmium pyrazolate 1∞[Ho(Pz)3(Pz)3] coordination polymer with a coordination number of 12.
Properties such as color or cooperative magnetism are a result of constitution, structural elements and phenomena like superexchange. Properties like luminescence are tunable by specific use of metals and ligands openign a construction kit system much like the synthetic methods for the generation of MOFs.
Our group has, among other compounds, successfully synthesized coordination polymers based on rare earth and various other metals, for example terbium triazolate 2∞[TbTz*3], which can undergo structural transitions at higher temperatures leading to the three-dimensional MOF.