Scintillating Metal‐Organic Frameworks: A New Class of Radiation Detection Materials

The detection and identification of subatomic particles is an important scientific problem with implications for medical devices, radiography, biochemical analysis, particle physics, and astrophysics. In addition, the development of efficient detectors of neutrons generated by fissile material is a pressing need for nuclear nonproliferation efforts. A critical objective in the field of radiation detection is to obtain the physical insight necessary for rational design of scintillation materials. Many factors affect the quantum efficiency and timing of scintillator light output, includingchemical composition, electronic structure, interchromophore interactions, crystal symmetry, and atomic density. None of the material types currently used in radiation detection, which include crystalline inorganic compounds such as LaBr3:Ce, organic compounds, and plastics, have the inherent synthetic versatility to exert systematic control over these factors. Therefore, it is likely that major advances in radiationdetectionwill requirethedevelopment of new materials outside the scope of traditional scintillators. Here, we propose that metal-organic frameworks (MOFs) could potentially offer the desired level of structural control, leading to an entirely new class of radiation detection materials. MOFs are crystalline materials consisting of metal clusters linked by coordinating organic groups. Yaghi, O’Keefe, and coworkers have shown that structures resulting from the selfassembly of specific metal ions and linkers can be predicted through an understanding of the geometric nets accessible to particular metal-linker combinations (‘‘reticular chemistry’’), [1‐3] which is difficult to accomplish in other extended crystalline materials such as zeolites and molecular solids. Furthermore, variation of the organic component of MOFs allows for additional structural modifications that can be used to tailor MOF properties. Conjugated organic molecules, which are usually fluorescent and are often scintillators as well, are used extensively as linkers in MOFs, and reports of fluorescent MOFs are increasing. [4‐9] The relatively rigid structure of some MOFs can create permanent nanoporosity, a property being explored for gas storage, [10‐15] separations, [13,16] catalysis, [13,17‐20] and sensing. [21‐23] This feature could also be advantageous in scintillation