Assembling a Heterobimetallic Actinide Metal‐Organic Framework by a Reaction‐Induced Preorganization Strategy

Abstract

Periodically arranging coordination‐distinct actinides into one crystalline architecture is intriguing but of great synthetic challenge. We report a rare example of a heterobimetallic actinide metal–organic framework (An‐MOF) by a unique reaction‐induced preorganization strategy. A thorium MOF (SCU‐16) with the largest unit cell among all Th‐MOFs was prepared as the precursor, then the uranyl was precisely embedded into the MOF precursor under oxidation condition. Single crystal of the resulting thorium‐uranium MOF (SCU‐16‐U) shows that a uranyl‐specific site was in situ induced by the formate‐to‐carbonate oxidation reaction. The heterobimetallic SCU‐16‐U exhibits multifunction catalysis properties derived from two distinct actinides. The strategy proposed here offers a new avenue to create mixed‐actinide functional material with unique architecture and versatile functionality.

Friends or Foes: Fundamental Principles of Th-Organic Scaffold Chemistry Using Zr-Analogs as a Guide

“…Broad chemical and thermal stability is one of the highly sought-after traits in the field of metal–organic frameworks (MOFs − ), which shapes the landscape of possible applications with a main focus on specific MOF classes, including those based on zirconium. − Indeed, Zr-MOFs (e.g., possessing fcu- , and ftw-type , topologies) exhibit excellent thermostability up to 500 °C, possess chemical stability across a wide pH range from 2 to 12, and demonstrate exceptional resilience even under 423 Gy/min γ radiation . At the same time, the recent and rapidly growing interest in the development of fuel cycle reactors, radiological daughters for nuclear medicine, and efficient nuclear stockpile recycling serves as the driving force for translating the wealth of fundamental knowledge acquired for Zr-MOFs to thorium-based analogs. − Since the onset of research focusing on Th-based materials, Zr-frameworks have been considered to be the closest analogs due to the shared metal oxidation state (+4), high Lewis acidity, formation of strong coordination bonds to carboxylate-based organic linkers, and oxophilicity comparable to thorium. − However, in contrast to a plethora of publications (>3600) focusing on Zr-MOFs, only around 100 exist for their Th-based counterparts (Figure ).…”

“…At the same time, the recent and rapidly growing interest in the development of fuel cycle reactors, radiological daughters for nuclear medicine, and efficient nuclear stockpile recycling serves as the driving force for translating the wealth of fundamental knowledge acquired for Zr-MOFs to thorium-based analogs. − Since the onset of research focusing on Th-based materials, Zr-frameworks have been considered to be the closest analogs due to the shared metal oxidation state (+4), high Lewis acidity, formation of strong coordination bonds to carboxylate-based organic linkers, and oxophilicity comparable to thorium. − However, in contrast to a plethora of publications (>3600) focusing on Zr-MOFs, only around 100 exist for their Th-based counterparts (Figure ). Moreover, less than 0.3% of these studies include any information on the reactivity of Th-based materials in a very narrow scope of reactions, targeting only six reaction classes. ,− Such disparity in the number of studies on zirconium-based versus thorium-based frameworks can be largely attributed to two main factors. For instance, the comprehensive fundamental understanding guiding the coordination chemistry of actinides is relatively underdeveloped in comparison with transition metals .…”

Mining for Metal–Organic Systems: Chemistry Frontiers of Th-, U-, and Zr-Materials

“…Rapidly expanding interest in areas like efficient nuclear stockpile recycling, development of effective nuclear fuel cycles, and preparation of isotopically pure radiological daughters for nuclear medicine has generated a rich scope of research surrounding actinide, including thorium (Th), chemistry. − At the same time, industrial demands in the energy and environmental sectors have brought solid-state actinide-based materials to the spotlight, with an emphasis on functional materials with high thermal and chemical stability. In this direction, metal–organic frameworks (MOFs) have recently attracted significant attention due to exceptional chemical, thermal, and mechanical stability, as well as structural integrity under γ radiation. − Design of Th-MOFs or any radioactive metal–organic compounds in general very often involves the use of nonradioactive surrogates as a first step, before transitioning to actinide-containing structures. Notably, employing nonradioactive surrogates is an important and accessible route toward studying actinides, and especially, transuranics, considering the additional licensing, advanced safety training, strict waste disposal, and even regulations limiting the quantity of radioactive compounds in a given laboratory.…”

Decorating Cage-Shaped Cavities with Carboxyl Groups on Two-Dimensional MOF Nanosheet for Trace Uranium(VI) Trapping

“…Traditional adsorbents, such as zeolites, clay, mesoporous carbon, and metals oxides, often suffer from slow adsorption kinetics, low adsorption selectivity, and capacities, which stems from their simple composition and lack of structural and functional tunability. ,− To achieve better adsorption performance for uranium, adsorbents with structural and functional tunability are highly desired, and adsorbent design with multiple factors should be considered, including surface area, porosity, and amount of adsorption sites. − Bearing this in mind, metal–organic frameworks (MOFs), a kind of crystalline hybrid porous material with a large surface area, densely populated chelating groups, and tunable pore structures, have been developed . The precisely designable and tailorable structures and components in MOFs are convenient to realize high performance in uranium extraction. − Amidoxime groups can be purposefully incorporated into UiO-66-NH-(AO) by a postsynthetic strategy, which showed good selectivity for uranium even in the presence of high concentrations of VO 2 2+ , Fe 3+ , Mg 2+ , Ca 2+ , and Zr 4+ . By introducing carboxyl and amidoxime groups into the MOF of MIL-101-SMA-AO, the elaborately constructed MOF exhibited ultrahigh uptake capacity (1086 mg/g) for uranium.…”