Metal Substitution into Metal Organic Nanotubes: Impacts on Solvent Uptake and Stability

Abstract

Transition metal dopants can be incorporated in metal organic frameworks to change the physical properties of the material. Metal organic nanotubes are a less well studied form of hybrid material, and in this study, transition metals were substituted into U(VI) metal organic nanotubes (UMON) to investigate changes with water uptake, solvent selectivity, and hydrostability. Single-crystal X-ray analysis, UV/vis spectroscopy, and electron microprobe analysis confirmed the substitution of (VO) 2+ , Co(II), Ni(II), Fe(II), and Cu(II), with the highest amount of incorporation by Cu(II). Water uptake and release by the substituted materials were similar to that of the pure UMON sample, with the exception in the Cu(II)-UMON samples, where less water present in the nanotubular cavities and additional heating were necessary for dehydration. A detailed investigation of the Cu(II)-UMON material indicated that the overall selectivity of the material was maintained and the hydrostability was drastically enhanced with incorporation. In the presence of ammonia, the pure and doped UMON material degraded to secondary phases.

Structural Engineering of Low‐Dimensional Metal–Organic Frameworks: Synthesis, Properties, and Applications

“…[140] As comparison, microcrystalline MOF-74 was formed in the absence of salicylic acid. Similarly, ROD-8 (Cd II ), [92] Co 5 (OH) 2 -(O 2 CCH 3 ) 8 ·2H 2 O nanowires, [141] NU-1000 rods, [142,143] U-based-MOF nanotubes, [99,144] In-porphyrin (Mn) hexagonal MOF rods, [53] and Cu-P,P′-diphenyl-diphosphinate (pcp)/1,2-bis(4-pyridyl)ethane) (bpye) nanorods [127] were synthesized by directing their corresponding reactions of specifically designed organic ligands and metal ions. More recently, Xu and co-workers fabricated conductive Cu-CAT nanowire arrays on carbon paper by adding carbon paper into the reaction solution of Cu(Ac) 2 ·H 2 O and 2,3,6,7, 10,11-hexahydroxytriphenylene (HHTP) (Figure 5e).…”

“…To date, a variety of MOFs with 1D structure, such as nanorods, [53,[90][91][92] nanotubes, [93][94][95][96][97][98][99] and nanofibers, [52,[100][101][102] have been synthesized and exhibited unique physicochemical properties. [38,103] As schematically illustrated in Figure 3, the current preparation strategies for 1D MOF architectures can be generally classified into two types, i.e., template and templatefree methods.…”

Exploring the unique water properties of metal-organic nanotubes

“…PXRD data (Figure 3.8 We previously observed if the UMON crystals were added to a solution containing NH3 dissolved in methanol, then the crystals dissolved and quickly reprecipitated as a secondary phase. 126 The rapid dissolution and re-precipitation resulted in poor crystal quality and the exact structure could not be determined using single crystal X-ray diffraction. We hypothesize that the NH3 is disrupting the hydrogen bonding network that stabilizes the 3-D crystalline lattice, resulting in the formation of…”

“…Albrecht-Schmitt et al 184 and Harrowfield et al, 185 where the introduction of Co 2+ or Ag + cations led to the formation of a highly porous 3D framework uranyl displays unique water uptake properties 62 and additional stability was achieved upon the addition of transition metal dopants. 126 We have also compared our the selectivity of our uranyl IDA nanotube to other similar compounds reported in the literature, notably the uranyl pyradinedicarboxylate (UPDC) [(UO2)(PDC)(H2O)](H2O)) nanoporous material synthesized by Thuery. [56][57][58]123 In our continued investigation of these materials, we sought to further understand chemical and physical changes of the…”

Development of metal organic materials for use in novel water treatment schemes

“…Unlike MOFs, the UMON displays a highly ordered ice-like array of water molecules located in the channel, reversible (37 °C) dehydration, stability in humid and higher temperature (<200 °C) environments, and specificity to water in both the liquid and vapor phase. 37 The main issue for the UMON compound is the use of mildly radioactive depleted uranium as the metal synthon, which will limit its implementation in advanced membrane technologies.…”