Multifaceted Modularity: A Key for Stepwise Building of Hierarchical Complexity in Actinide Metal–Organic Frameworks

Abstract

Growing necessity for efficient nuclear waste management is a driving force for development of alternative architectures toward fundamental understanding of mechanisms involved in actinide (An) integration inside extended structures. In this manuscript, metal-organic frameworks (MOFs) were investigated as a model system for engineering radionuclide containing materials through utilization of unprecedented MOF modularity, which cannot be replicated in any other type of materials. Through the implementation of recent synthetic advances in the MOF field, hierarchical complexity of An-materials was built stepwise, which was only feasible due to preparation of the first examples of actinide-based frameworks with "unsaturated" metal nodes. The first successful attempts of solid-state metathesis and metal node extension in An-MOFs are reported, and the results of the former approach revealed drastic differences in chemical behavior of extended structures versus molecular species. Successful utilization of MOF modularity also allowed us to structurally characterize the first example of bimetallic An-An nodes. To the best of our knowledge, through combination of solid-state metathesis, guest incorporation, and capping linker installation, we were able to achieve the highest Th wt % in mono- and biactinide frameworks with minimal structural density. Overall, the combination of a multistep synthetic approach with homogeneous actinide distribution and moderate solvothermal conditions could make MOFs an exceptionally powerful tool to address fundamental questions responsible for chemical behavior of An-based extended structures and, therefore, shed light on possible optimization of nuclear waste administration.

Formation of a new type of uranium(iv) poly-oxo cluster {U38} based on a controlled release of water via esterification reaction

“… 32 , 33 Such a hexameric moiety is also encountered as a secondary building unit in the three-dimensional construction of metal–organic frameworks with ditopic carboxylate linkers (Th and U). 34 – 38 There exist very few motifs with higher nuclearities with Th( iv ) ({Th 8 } and {Th 9 } 39 ), whereas the exploration in the uranium system revealed the identification of many polynuclear oligomers such as {U 10 }, 40 {U 12 }, 22 , 41 {U 16 } 40 and {U 38 }. 6 The latter species have been synthesized by using coordinating ligands, such as benzoate or triflate, in different organic solvents (acetonitrile and tetrahydrofuran) together with the control of water content in the system to monitor the condensation process, leading to the formation of poly-oxo clusters with these different high nuclearities.…”

A robust Th-azole framework for highly efficient purification of C2H4 from a C2H4/C2H2/C2H6 mixture

“…However, due to the easy-to-hydrolysis nature of both Cr(III) and Zr(IV), it is still difficult to synthesize Cr(III) and Zr(IV) MOFs with high crystallization. Alternatively, another high-valence metal ion of Th(IV) shows less hydrolytic nature, suggesting an optimal metal ion to generate stable MOFs [52][53][54][55][56] . Generally speaking, according to the hard and soft acid and bases (HSAB) principle, the Zr-based or Th-based MOFs are usually constructed by O-donor carboxylic ligands.…”

Emergence of Uranium as a Distinct Metal Center for Building Intrinsic X‐ray Scintillators

“…The dense framework, as well as the inert nature of uranyl carboxylate bonds, endow SCU‐9 with good thermal stability and hydrolytic stability, similar to many reported uranyl MOFs –. Specifically, SCU‐9 is stable after immersion into aqueous solution with pH ranging from 2 to 12, as shown in the Supporting Information, Figures S3 and S4.…”