We confirm that the investigated Al-MOFs are robust with respect to reproducible synthesis and concomitant porosity as a prerequisite for applications.
The
solid-solution mixed-linker approach, where a linker is partially
replaced by a similar one under retention of the isoreticular metal–organic
framework (MOF) structure, offers an easy and inexpensive way to fine-tune
MOF properties to design tailored compounds. A total of 10 aluminum
mixed-linker MOFs, [Al(OH)(X)
a
(Y)1–a
] (X = IPA, isophthalate; Y = FDC,
2,5-furandicarboxylate) spanning between the isostructural MOFs CAU-10-H
(a = 1) and MIL-160 (a = 0), were
synthesized by employing different ratios of the aforementioned linkers.
CAU-10-H and MIL-160 have been reported as highly promising materials
for cycling water sorption for heat transformation applications. A
detailed characterization with a focus on the changes in the sorption
properties for water vapor showed that the hydrophilicity is readily
and easily tuned through the mixed-linker approach between the limits
of MIL-160 and CAU-10-H. An increasing fraction of IPA shifts the
steep increase in the S-shaped water adsorption isotherm in small
steps from p/p
0 = ∼0.05
for MIL-160 to p/p
0 =
∼0.18 for CAU-10-H. Higher coefficient of performance (COPH) values for the mixed-linker materials over MIL-160 illustrate
the well-balanced hydrophobicity/hydrophilicity of the former under
the exemplary calculation conditions.
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.
Microwave-assisted dry-gel conversion (MW-DGC) combines the advantages of concentrated reactants in DGC with fast heating by microwave irradiation. This novel combination allows drastically decreasing the amount of solvent needed for synthesis and reaction times with the energy needed. Furthermore, MW-DGC allows for the recovery and re-use of the reaction solvent and thereby can significantly reduce the overall solvent waste in the syntheses of the four important MOFs MIL-100(Fe) (Basolite F300), UiO-66, MIL-140A and aluminium fumarate (Alfum, Basolite A520). All the MOF products obtained from MW-DGC showed satisfying yields, crystallinity and porosity in comparison with the industrial benchmarks Basolite F300 and Basolite A520. Moreover, MW-DGC also advantageously leads to a hierarchical micro-mesoporous Alfum material different to that from other synthesis methods.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.