Metal–organic
frameworks (MOFs) currently receive high interest
for cycling water adsorption applications like adsorption heat transformation
for air-conditioning purposes. For practical use in adsorption heat
pumps (AHPs), the microcrystalline powders must be formulated such
that their high porosity and pore accessibility are retained. In this
work, the preparation of millimeter-scaled pellets of MIL-160(Al),
Al-fumarate (Basolite A520), UiO-66(Zr), and Zr-fumarate (MOF-801)
is reported by applying the freeze granulation method. The use of
poly(vinyl alcohol) (PVA) as a binder reproducibly resulted in highly
stable, uniformly shaped PVA/MOF pellets with 80 wt % MOF loading,
with essentially unchanged MOF porosity properties after shaping.
The shaped pellets were analyzed for the application in AHPs by water
adsorption isotherms, over 1000 water adsorption/desorption cycles,
and thermal and mechanical stability tests. Furthermore, the Al-fum
pellets were applied in a fixed-bed, full-scale heat exchanger, yielding
specific cooling powers from 349 up to 431 W/kg (adsorbent), which
outperforms the current commercially used silica gel grains in AHPs
under comparable operating conditions.
Background:
In the last decades, 3D-printing has been investigated and used intensively in the field of
tissue engineering, automotive and aerospace. With the first FDA approved printed medicinal product in 2015,
the research on 3D-printing for pharmaceutical application has attracted the attention of pharmaceutical scientists.
Due to its potential of fabricating complex structures and geometrics, it is a highly promising technology for
manufacturing individualized dosage forms. In addition, it enables the fabrication of dosage forms with tailored
drug release profiles.
Objective:
The aim of this review article is to give a comprehensive overview of the used 3D-printing techniques
for pharmaceutical applications, including information about the required material, advantages and disadvantages
of the respective technique.
Methods:
For the literature research, relevant keywords were identified and the literature was then thoroughly
researched.
Conclusion:
The current status of 3D-printing as a manufacturing process for pharmaceutical dosage forms was
highlighted in this review article. Moreover, this article presents a critical evaluation of 3D-printing to control the
dose and drug release of printed dosage forms.
Surface
halogenation is an important means to tune or improve functionalities
of solid-state materials. However, this concept has been hardly explored
and exploited in the engineering of metal-organic frameworks (MOFs).
Here, a facile approach to obtain halo-functionalized derivatives
of zirconium fumarate (MOF-801) is developed by reacting zirconium
halides (ZrX4; X = Cl, Br, I) in water with acetylenedicarboxylic
acid. The latter quantitatively undergoes an unusual in situ linker
transformation into halofumarate via trans addition of HX to the −CC–
triple bond. This HX addition and MOF formation happen in a one-pot
reaction, that is, the in situ generated halogenated linker reacts
with zirconium ions in solution to yield three microporous HHU-2-X
MOFs (X = Cl, Br, I) with an fcu topology, containing
UiO-type [Zr6O4(OH)4] secondary building
units 12-fold connected by halofumarate linkers. The halogen (Cl)
groups in HHU-2-Cl result in increased hydrophilicity for water vapor
sorption as well as increased gas uptakes of 21% SO2, 24%
CH4, 44% CO2, and 154% N2 when compared
to the non-halogenated MOF-801. The tuning of the inner surface chemistry
is realized to yield multipurpose adsorbent materials for enhanced
gas and vapor uptakes over their non-halogenated analogues. The gas
sorption properties of the chlorinated HHU-2-Cl material indicate
its suitability for CO2, N2, and SO2 capture and separation, while its water sorption profile yields
a high heat storage capacity of 500 kJ kg–1, making
it promising for adsorption-based thermal batteries and dehumidification
applications.
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