Unveiling the Unique Roles of Metal Coordination and Modulator in the Polymorphism Control of Metal-Organic Frameworks.

Polymorphism control of metal-organic frameworks is highly desired for elucidating structure-property relationship, but remains an empirical process and is usually done in a trial-and-error approach. Herein, we adopt the rarely touched actinide cation Th 4+ and a ditopic linker to construct a series of thorium-organic frameworks (TOFs) with a range of polymorphs. The extraordinary coordination versatility of Th 4+ cations and clusters, coupled with synthetic modulation, renders five distinct phases, wherein the highest degree of interpenetration (3-fold) and porosity (75.9%) of TOFs have been achieved. Notably, the O atom on the capping site of the nine-coordinated Th 4+ cation can function as a bridging unit to interconnect neighboring SBUs, affording topologies undocumented for other tetravalent metal containing MOFs. Furthermore, HCOOH has been demonstrated as a bridging unit of SBUs to further induce structural complexity. The resulting TOFs exhibit considerably different adsorption behaviors toward organic dyes, suggesting that TOFs represent an exceptional and promising platform for structure-property relationship study.