期刊
ACS APPLIED MATERIALS & INTERFACES
卷 13, 期 19, 页码 22485-22494出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c03717
关键词
ammonia capture; chemical separation; metal-organic framework; reversible uptake; irreversible uptake; charge-compensating anions
资金
- U.S. Department of Energy (DOE) Office of Science, Basic Energy Sciences [DE-FG02-08ER15967]
- Defense Threat Reduction Agency [HDTRA1-18-1-0003]
- MRSEC program of the National Science Foundation at the Materials Research Center of Northwestern University [DMR-1121262]
- Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource [NSF NNCI-1542205]
- MRSEC program at the Materials Research Center [NSF DMR1121262]
- International Institute for Nanotechnology (IIN)
- Keck Foundation
- State of Illinois, through the IIN
- DOE [DE-SC0001329]
The study found that NU-1000-Cl has enhanced capacity for both reversible and irreversible uptake of ammonia compared to the chloride-free version. The presence of chloride ions also facilitates irreversible reactions between ammonia and NU-1000-Cl. The chemical interactions between ammonia and NU1000-Cl result in the separation of NH3 from N-2 at room temperature.
Ammonia capture by porous materials is relevant to protection of humans from chemical threats, while ammonia separation may be relevant to its isolation and use following generation by emerging electrochemical schemes. Our previous work described both reversible and irreversible interactions of ammonia with the metal-organic framework (MOF) material, NU-1000, following thermal treatment at either 120 or 300 degrees C. In the present work, we have examined NU-1000-Cl, a variant that features a modified node structure-at ambient temperature, Zr-6(mu(3)-O)(4)(mu(3)-OH)(4)(H2O)(8)(12+) in place of Zr-6(mu(3)-O)(4)(mu(3)-OH)(4)(OH)(4)(H2O)(4)(8+). Carboxylate termini from each of eight linkers balance the 8+ charge of the parent node, while four chloride ions, attached only by hydrogen bonding, complete the charge balance for the 12+ version. We find that both reversible and irreversible uptake of ammonia are enhanced for NU-1000-Cl, relative to the chloride-free version. Two irreversible interactions were observed via in situ diffuse-reflectance infrared Fourier-transform spectroscopy: coordination of NH3 at open Zr sites generated during thermal pretreatment and formation of NH4+ by proton transfer from node aqua ligands. The irreversibility of the latter appears to be facilitated by the presence chloride ions, as NH4+ formation occurs reversibly with chloride-free NU-1000. At room temperature, chemically reversible (and irreversible) interactions between ammonia and NU1000-Cl result in separation of NH3 from N-2 when gas mixtures are examined with breakthrough instrumentation, as evinced by a much longer breakthrough time (similar to 9 min) for NH3.
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