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DOE OSTI2020

Anion-exchanged and quaternary ammonium functionalized MIL-101-Cr metal-organic framework (MOF) for ReO 4 – /TcO 4 – sequestration from groundwater

There are few effective technologies for the sequestration of highly water-soluble pertechnetate (TcO 4 – ) from contaminated water despite the urgency of environmental and public health concerns. Here, anion exchanged and cetyltrimethylammonium bromide (CTAB) functionalized MIL-101-Cr-NO 3 were investigated for perrhenate (ReO 4 – ), a surrogate of TcO 4 – , sequestration from artificial groundwater. Cl – , I – , and CF 3 SO 3 – exchanged MIL-101-Cr proved more effective at ReO 4 – removal than the parent MIL-101-Cr-F. Compared to the parent framework, CTAB functionalized MIL-101-Cr-NO 3 increased ReO 4 – removal capacity from 39 to 139 mg/g, improved the reaction kinetics from ~30 to <10 min to reach full adsorption capacity and the selectivity for ReO 4 – over competing NO 3 – , CO 3 2– , SO 4 2– , and Cl – . Spectroscopic data indicated that the chemical speciation of Re in the exchanged MIL-101-Cr remained ReO 4 – , indicating synergistic sequestration through both anion exchange and non-ion exchange binding with the positively charged ligand of CTAB. These studies foreshadow potential applications of MOFs for the remediation of 99 TcO 4 – from contaminated environments.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2020

Materials Data on CrF2 by Materials Project

CrF2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Cr2+ is bonded to six equivalent F1- atoms to form a mixture of edge and corner-sharing CrF6 octahedra. The corner-sharing octahedra tilt angles range from 48–56°. There are four shorter (2.04 Å) and two longer (2.48 Å) Cr–F bond lengths. F1- is bonded in a distorted trigonal planar geometry to three equivalent Cr2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Cr2F5 by Materials Project

Cr2F5 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Cr+2.50+ sites. In the first Cr+2.50+ site, Cr+2.50+ is bonded in a distorted square co-planar geometry to six F1- atoms. There are a spread of Cr–F bond distances ranging from 2.00–2.67 Å. In the second Cr+2.50+ site, Cr+2.50+ is bonded to six F1- atoms to form corner-sharing CrF6 octahedra. The corner-sharing octahedral tilt angles are 30°. There is two shorter (1.93 Å) and four longer (1.96 Å) Cr–F bond length. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a bent 150 degrees geometry to two Cr+2.50+ atoms. In the second F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent Cr+2.50+ atoms. In the third F1- site, F1- is bonded in a 3-coordinate geometry to three Cr+2.50+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CrF3 by Materials Project

CrF3 crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Cr3+ is bonded to six equivalent F1- atoms to form corner-sharing CrF6 octahedra. The corner-sharing octahedral tilt angles are 36°. All Cr–F bond lengths are 1.95 Å. F1- is bonded in a bent 150 degrees geometry to two equivalent Cr3+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CrF5 by Materials Project

CrF5 crystallizes in the orthorhombic Pbcm space group. The structure is one-dimensional and consists of two CrF5 ribbons oriented in the (1, 0, 0) direction. Cr5+ is bonded to six F1- atoms to form corner-sharing CrF6 octahedra. The corner-sharing octahedral tilt angles are 37°. There are a spread of Cr–F bond distances ranging from 1.73–1.98 Å. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Cr5+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Cr5+ atom. In the third F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent Cr5+ atoms. In the fourth F1- site, F1- is bonded in a single-bond geometry to one Cr5+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CrF5 by Materials Project

CrF5 crystallizes in the monoclinic P2_1/c space group. The structure is one-dimensional and consists of two CrF5 ribbons oriented in the (0, 0, 1) direction. Cr5+ is bonded to six F1- atoms to form corner-sharing CrF6 octahedra. The corner-sharing octahedral tilt angles are 32°. There are a spread of Cr–F bond distances ranging from 1.75–1.92 Å. There are five inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Cr5+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Cr5+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one Cr5+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one Cr5+ atom. In the fifth F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent Cr5+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CrF6 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CrF4 by Materials Project

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CrF4 by Materials Project

36 MATERIALS SCIENCE↗