Zirconium Metal–Organic Frameworks Integrating Chloride Ions for Ammonia Capture and/or Chemical Separation

Abstract

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 °C. In the present work, we have examined NU-1000-Cl, a variant that features a modified node structure–at ambient temperature, Zr6(μ3-O)4(μ3-OH)4(H2O)8 12+ in place of Zr6(μ3-O)4(μ3-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 NU-1000-Cl result in separation of NH3 from N2 when gas mixtures are examined with breakthrough instrumentation, as evinced by a much longer breakthrough time (∼9 min) for NH3.

Product Inhibition and the Catalytic Destruction of a Nerve Agent Simulant by Zirconium-Based Metal–Organic Frameworks

“…MOFs, consisting of metal-based nodes connected by polytopic organic linkers, are a class of hybrid materials characterized by high tunability, − crystallinity, , porosity, , multifunctionality, − and site uniformity. , Many present readily accessible catalytic sites. , Zirconium-based MOFs have shown outstanding chemical (between pH ∼1–11) and thermal (up to 500 °C) stability. , Specifically, Zr 6 -based MOFs ( e.g. , NU-1000, UiO-66, and MOF-808) featuring reactive or displaceable −OH and −OH 2 ligands and Zr-OH-Zr linkages, which are structurally reminiscent of the Zn-OH-Zn-containing active site of PTE, show remarkable catalytic activity for hydrolysis of CWAs, such as GB and GD, and their simulants, such as methyl paraoxon (Figure ), also known as dimethyl-4-nitrophenyl phosphate (DMNP). ,,, One metal in the M-OH-M site coordinately binds to the double-bonded oxygen, thereby weakening the PO bond and indirectly weakening (activating) the targeted P–X bond.…”

Highly Dispersed Ionic Liquids in Mesoporous Molecular Sieves Enable a Record NH3 Absorption

“…21 The XPS data supported the above FT-IR results and further explained why ammonia could not be completely desorbed. 82 These results reveal that the highly efficient adsorption of NH 3 was mainly attributed to the NH 3 coordination to Zn cation and the hydrogen-bonding interaction of NH 3 with Cl of [C 1 NH 3 ][Zn 3 Cl 7 ], although FDU-12 also had a minor contribution to ammonia adsorption.…”

Insights into dual-functional modification for water stability enhancement of mesoporous zirconium metal–organic frameworks

“…Our previous studies have shown that the aqua/hydroxo ligands in NU-1000 can behave as displaceable site-holders for graing non-structural ligands, 37,38 as reactive sites for immobilizing metal cations, [39][40][41][42] and as charge-compensating hydrogen bonding sites for noncovalently immobilizing halide ions. 14,43 Each of three candidate nonstructural ligands, acetylacetonate (Acac À ), 1,1,1-tri-uoroacetylacetonate (TFacac À ), or hexauoroacetylacetonate (Facac À ) was graed, via SALI (solvent-assisted ligand incorporation), onto Zr 6 -oxy nodes (Fig. 1).…”