Reaction of CuCl(2) x 2 H(2)O with 1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene (H(3)BTTri) in DMF at 100 degrees C generates the metal-organic framework H(3)[(Cu(4)Cl)(3)(BTTri)(8)(DMF)(12)] x 7 DMF x 76 H(2)O (1-DMF). The sodalite-type structure of the framework consists of BTTri(3-)-linked [Cu(4)Cl](7+) square clusters in which each Cu(II) center has a terminal DMF ligand directed toward the interior of a large pore. The framework exhibits a high thermal stability of up to 270 degrees C, as well as exceptional chemical stability in air, boiling water, and acidic media. Following exchange of the guest solvent and bound DMF molecules for methanol to give 1-MeOH, complete desolvation of the framework at 180 degrees C generated H(3)[(Cu(4)Cl)(3)(BTTri)(8)] (1) with exposed Cu(II) sites on its surface. Following a previously reported protocol, ethylenediamine molecules were grafted onto these sites to afford 1-en, featuring terminal alkylamine groups. The N(2) adsorption isotherms indicate a reduction in the BET surface area from 1770 to 345 m(2)/g following grafting. The H(2) adsorption data at 77 K for 1 indicate a fully reversible uptake of 1.2 wt % at 1.2 bar, while the CO(2) isotherm at 195 K shows a maximal uptake of 90 wt % at 1 bar. Compared to 1, the alkylamine-functionalized framework 1-en exhibits a higher uptake of CO(2) at 298 K and pressures up to ca. 0.1 bar, as well as a higher CO(2)/N(2) selectivity at all measured pressures. Significantly, 1-en also exhibits an isosteric heat of CO(2) adsorption of 90 kJ/mol, which is much higher than the 21 kJ/mol observed for 1. This chemisorption interaction is the strongest reported to date for a metal-organic framework and points toward the potential utility of alkylamine-appended frameworks for the postcombustion capture of CO(2) from low-pressure flue gas streams.
Stable nanoparticles dispersions of the porous hybrid MIL-101(Cr) allow dip-coating of high quality optical thin films with dual hierarchical porous structure. Moreover, for the first time, mechanical and sorption properties of mesoporous MOFs based thin films are evaluated.
Acoustic
vibrations of small nanoparticles are still ruled by continuum
mechanics laws down to diameters of a few nanometers. The elastic
behavior at lower sizes (<1–2 nm), where nanoparticles become
molecular clusters made by few tens to few atoms, is still little
explored. The question remains to which extent the transition from
small continuous-mass solids to discrete-atom molecular clusters affects
their specific low-frequency vibrational modes, whose period is classically
expected to linearly scale with diameter. Here, we investigate experimentally
by ultrafast time-resolved optical spectroscopy the acoustic response
of atomically defined ligand-protected metal clusters Au
n
(SR)
m
with a number n of atoms ranging from 10 to 102 (0.5–1.5 nm diameter
range). Two periods, corresponding to fundamental breathing- and quadrupolar-like
acoustic modes, are detected, with the latter scaling linearly with
cluster diameters and the former taking a constant value. Theoretical
calculations based on density functional theory (DFT) predict in the
case of bare clusters vibrational periods scaling with size down to
diatomic molecules. For ligand-protected clusters, they show a pronounced
effect of the ligand molecules on the breathing-like mode vibrational
period at the origin of its constant value. This deviation from classical
elasticity predictions results from mechanical mass-loading effects
due to the protecting layer. This study shows that clusters characteristic
vibrational frequencies are compatible with extrapolation of continuum
mechanics model down to few atoms, which is in agreement with DFT
computations.
The melting behavior of a coordination polymer (CP) crystal was utilized to achieve enhanced and optically switchable proton conductivity in the solid state. The strong acid molecules (triflic acid) were doped in one-dimensional (1D) CP, [Zn(HPO )(H PO ) ](ImH ) (ImH =monoprotonated imidazole) in the melt state, and overall enhancement in the proton conductivity was obtained. The enhanced proton conductivity is assigned to increased number of mobile protons and defects created by acid doping. Optical control over proton conductivity in the CP is achieved by doping of the photo acid molecule pyranine into the melted CP. The pyranine reversibly generates the mobile acidic protons and local defects in the glassy state of CP resulting in the bulk switchable conductivity mediated by light irradiation. Utilization of CP crystal in liquid state enables to be a novel route to incorporate functional molecules and defects, and it provides a tool to control the bulk properties of the CP material.
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