Showing papers by "Praveen K. Thallapally published in 2022"

Self-Adjusting Metal-Organic Framework for Efficient Capture of Trace Xenon and Krypton.

Abstract: The capture of the xenon and krypton from nuclear reprocessing off-gas is essential to the treatment of radioactive waste. Although various porous materials have been employed to capture Xe and Kr, the development of high-performance adsorbents capable of trapping Xe/Kr at very low partial pressure as in the in the nuclear reprocessing off-gas conditions remains challenging. Herein, we report a self-adjusting metal-organic framework based on multiple weak binding interactions to capture trace Xe and Kr from the nuclear reprocessing off-gas. The self-adjusting behavior of ATC-Cu and its mechanism have been visualized by the in-situ single-crystal X-ray diffraction studies and theoretical calculations. The self-adjusting behavior endows ATC-Cu unprecedented uptake capacities of 2.65 and 0.52 cm 3 g -1 for Xe and Kr respectively at 0.1 bar and 298 K, as well as the record Xe capture capability from the nuclear reprocessing off-gas. Our work not only provides a benchmark Xe adsorbent but proposes a new route to construct smart materials for efficient separations.

Self‐Adjusting Metal‐Organic Framework for Efficient Capture of Trace Xenon and Krypton

Abstract: The capture of the xenon and krypton from nuclear reprocessing off-gas is essential to the treatment of radioactive waste. Although various porous materials have been employed to capture Xe and Kr, the development of high-performance adsorbents capable of trapping Xe/Kr at very low partial pressure as in the nuclear reprocessing off-gas conditions remains challenging. Herein, we report a self-adjusting metal-organic framework based on multiple weak binding interactions to capture trace Xe and Kr from the nuclear reprocessing off-gas. The self-adjusting behavior of ATC-Cu and its mechanism have been visualized by the in-situ single-crystal X-ray diffraction studies and theoretical calculations. The self-adjusting behavior endows ATC-Cu unprecedented uptake capacities of 2.65 and 0.52 mmol g−1 for Xe and Kr respectively at 0.1 bar and 298 K, as well as the record Xe capture capability from the nuclear reprocessing off-gas. Our work not only provides a benchmark Xe adsorbent but proposes a new route to construct smart materials for efficient separations.

Monitoring Xenon Capture in a Metal Organic Framework Using Laser-Induced Breakdown Spectroscopy

Abstract: Molten salt reactor operation will necessitate circulation of a cover gas to remove certain evolved fission products and maintain an inert atmosphere. The cover gas leaving the reactor core is expected to contain both noble and non-noble gases, aerosols, volatile species, tritium, and radionuclides and their daughters. To remove these radioactive gases, it is necessary to develop a robust off-gas system, along with novel sensors to monitor the gas stream and the treatment system performance. In this study, a metal organic framework (MOF) was engineered for the capture of Xe, a major contributor to the off-gas source term. The engineered MOF column was tested with a laser-induced breakdown spectroscopy (LIBS) sensor for noble gas monitoring. The LIBS sensor was used to monitor breakthrough tests with various Xe, Kr, and Ar mixtures to determine the Xe selectivity of the MOF column. This study offers an initial demonstration of the feasibility of monitoring off-gas treatment systems using a LIBS sensor to aid in the development of new capture systems for molten salt reactors.

Noble Gas Management: SBMOF 1 vs. NUCON Carbon

Abstract: for the high surface area sample along with a separate sample of SBMOF-1 that had a measured surface area of ~120 m 2 /g. The data obtained show a quick uptake of Xe at low pressures, saturating around 1.45 mmol/g, which is nearly identical to previously reported data for SBMOF-1 despite the increase in surface area and is slightly higher than the lower surface area sample. The Kr adsorption was not as high at low pressure as the Xe uptake in that range and it saturated near 0.9 mmol/g, which is also close to the low surface area sample.

Self‐Assembly and Oriented Growth of Conductive Ni‐CAT‐1 Metal‐Organic Framework at Solid–Liquid Interfaces

Abstract: Two‐dimensional (2D) conductive metal‐organic frameworks (MOF) represent a unique class of electrode materials with high capacity and power density. Understanding molecular mechanisms and pathways for heterogeneous nucleation of 2D π‐conjugated MOFs is highly desirable for controlling the structure and properties of conductive MOFs on solid substrates. Herein, a systematic study of nucleation and growth of 2D π‐conjugated Ni‐catecholate (Ni‐CAT‐1) MOFs on highly oriented pyrolytic graphite (HOPG) and copper substrates is reported. It is discovered that the nucleation density and growth kinetics of the MOF film can be controlled by varying substrate interactions with the organic linker. Specifically, π–π interactions between the linker and the HOPG dictate lower nucleation density, whereas π–metal interactions between the linker and the copper substrate dictate faster nucleation and higher nucleation densities. These studies reveal the key mechanism for Ni‐CAT‐1 nucleation on different surfaces and provide insights into interfacial control over the growth of other 2D π‐conjugated MOF films on solid substrates to inform synthesis of functional materials.

Porous Liquids as Electrolyte: A Case Study of Li+ and Mg2+ Ion Transport in Crown Ether-Based Type-II Porous Liquids

Abstract: We demonstrated an enhanced ion transport properties of type-II porous liquid-based electrolyte in which crown ether provides internal porosity and are capable of coordinating and transporting Li+ and Mg2+ ions. We investigated the solvation structure and transport properties of the porous liquid electrolytes with different functional groups and cavity sizes. Among the electrolytes studied, the 12-crown-4 (12C4)-based porous liquid electrolyte exhibited the most enhanced ionic conductivity due to size match between the crown ether cavity and the Li+ ion. Nuclear magnetic resonance and Fourier transform infrared analyses revealed that addition of crown ethers reduces the Li+ ion–solvent interaction, resulting in the formation of Li-crown ether complexes. Molecular simulations complement such observations by describing the detailed solvation environment at molecular scale, including complexation between Li+ and Mg2+ ions and 12C4. The strategy described here using crown ether-based porous liquids should be applicable to design versatile electrolytes for various metal-ion batteries.

Computation-informed optimization of Ni(PyC)2 functionalization for noble gas separations

Abstract: Our objective is to tune a “lead” metal-organic framework, Ni(PyC)2 (pyridine-4-carboxylate [PyC]), by functionalizing its PyC ligands to maximize its adsorptive selectivity for xenon over krypton at room temperature. To guide experiments, we (1) construct a library of Ni(PyC-X)2 (X = functional group) crystal structure models then (2) use molecular simulations to predict their noble gas adsorption and selectivity at room temperature. Motivated by our virtual screening, we synthesize Ni(PyC-m-NH2)2, determine its crystal structure by X-ray powder diffraction, measure its Xe, Kr, and Ar adsorption isotherms (298 K), and indeed find that its dilute Xe/Kr selectivity at 298 K (20) exceeds that of its parent Ni(PyC)2 (17). Corroborated by molecular models, in situ X-ray diffraction shows that Ni(PyC-m-NH2)2 organizes well-defined, Xe-tailored binding pockets along its one-dimensional channels. Our study illustrates the computation-informed optimization of a “lead” metal-organic framework.