Water and ethanol stabilities of the crystal structure of the Cu-based metal-organic framework (MOF) HKUST-1 have been investigated. Vapour (water and ethanol) sorption isotherms and cyclability were measured by a dynamic strategy. The ethanol sorption capacity of HKUST-1 at 303 K remained unchanged contrasting water sorption (which decreased along with the sorption experiment time). Considering the binding energy of each sorbate with the open Cu(ii) sites, obtained by the use of diffusion coefficients, we showed the superior crystal stability of the HKUST-1 framework towards ethanol. Finally, a small quantity of ethanol (pre-adsorbed) slightly enhanced CO capture without crystal structure degradation.
Synthesis
of a new HKUST-1 composite based on single-walled carbon
nanotubes (SWCNTs) was successfully achieved (SWCNT@HKUST-1). SWCNTs
were used as templates to grow rod-like HKUST-1 crystals over the
surface of the nanotubes. N
2
adsorption properties showed
an increment on the surface area and pore volume for the SWCNT@HKUST-1
composite. Furthermore, the CO
2
capture increased, from
7.92 to 8.75 mmol g
–1
at 196 K up to 100 kPa, for
the SWCNT@HKUST-1 composite. This enhancement was directly associated
with the increase of the surface area of the composite. Additionally,
an increase in the CO
2
heat of adsorption was estimated,
from 30 to 39.1 kJ mol
–1
for the SWCNT@HKUST-1 composite.
In situ Raman experiments corroborated the favored CO
2
adsorption
for the composite and provided an insight into the augmented hydrophobicity
of the SWCNT@HKUST-1. Ethanol adsorption isotherms corroborated an
increase in the hydrophobicity of the material upon the incorporation
of carbon nanotubes.
The
water-stable material NOTT-401 was investigated for CO
2
capture under humid conditions. Water adsorption properties
of NOTT-401 were studied, and their correlation with CO
2
sequestration at different relative humidities (RHs) showed that
the CO
2
capture increased from 1.2 wt % (anhydrous conditions)
to 3.9 wt % under 5% RH at 30 °C, representing a 3.2-fold improvement.
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