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.

MIL-53(Al)-TDC shows good hydrothermal stability and desirable water sorption properties for heat transformation applications.

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.

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 −CC– 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.

The amino group in the MOF NH 2 -MIL-101(Cr) was postsynthetically converted into urea-groups partially using either ethyl isocyanatoacetate, furfuryl isocyanate, p-toluenesulfonyl isocyanate or 3-(triethoxysilyl)propyl isocyanate in acetonitrile. The derived four novel urea-MOFs exhibit the expected lower BET surface areas and pore volumes than MIL-101(Cr) and NH 2 -MIL-101(Cr) MOFs but the partially p-toluenesulfonyl-ureamodified MOF exhibits an outstanding SO 2 adsorption capacity of 823 cm 3 g À 1 (corresponding to 36.7 mmol g À 1 or 70 wt.% at T = 0°C and 0.9 bar), which is the second highest SO 2 uptake of any known material today -surprisingly even better than for highly porous MIL-101(Cr) with an uptake of 645 cm 3 g À 1 SO 2 under the same conditions. The high uptake is linked to the favorable dipole interactions of SO 2 with the sulfonyl group of the p-toluenesulfonyl-modified MOF.

The report is the first broader evaluation of the gas sorption properties of CAU-23 for the adsorptives CO 2 , H 2 , CH 4 , and SO 2 . CAU-23 is of intermediate porosity among Al-MOFs with specific BET surface areas of the order of MIL-100 > MIL-53 > CAU-23 > MIL-160 > MIL-53-TDC > Alfum > CAU-10-H and total pore volumes of the order of MIL-100 > MIL-53 > CAU-23 > Alfum = MIL-160 > MIL-53-TDC > CAU-10-H. CO 2 uptake (3.97 mmol g À 1 , 293 K) and H 2 uptake (10.25 mmol g À 1 , 77 K) of CAU-23 are second in the series and only slightly smaller than for MIL-160. The CH 4 uptake of CAU-23 (0.89 mmol g À 1 , 293 K) is unremarkable in comparison with the other Al-MOFs. The SO 2 uptake (8.4 mmol g À 1 , 293 K) follows the porosity and higher SO 2 uptakes were only observed for MIL-53 and MIL-100. CAU-23 is one of the best Al-MOFs for high-pressure sorption of CO 2 , with an uptake of 33 wt.-% at 20 bar, 293 K. Gas sorption measurements at two different temperatures gave near zero-coverage enthalpy of adsorptions, ~Hads 0 for CO 2 of À 22 kJ mol À 1 and of SO 2 for À 38 kJ mol À 1 which is at the low end of the other Al-MOFs (À 22 to À 39 kJ mol À 1 for CO 2 ; À 41 to À 51 kJ mol À 1 for SO 2 ), yet ~Hads increases for CAU-23 with CO 2 and SO 2 to À 25 and À 57 kJ mol À 1 , respectively. For CO 2 /CH 4 and SO 2 /CO 2 separation, ideal adsorbed solution theory (IAST) predicted gas selectivities of 5 and 27-50 (depending on molar ratio and model), respectively, in line with 4.5-6.3 and 17-50, respectively, with most of the other Al-MOFs, where only MIL-53-TDC with 83 and MIL-160 with 126 gave a higher SO 2 /CO 2 selectivity at a molar ratio of 0.5.