Programming MOFs for water sorption: amino-functionalized MIL-125 and UiO-66 for heat transformation and heat storage applications

Abstract

Sorption-based heat transformation and storage appliances are very promising for utilizing solar heat and waste heat in cooling or heating applications. The economic and ecological efficiency of sorption-based heat transformation depends on the availability of suitable hydrophilic and hydrothermally stable sorption materials. We investigated the feasibility of using the metal-organic frameworks UiO-66(Zr), UiO-67(Zr), H2N-UiO-66(Zr) and H2N-MIL-125(Ti) as sorption materials in heat transformations by means of volumetric water adsorption measurements, determination of the heat of adsorption and a 40-cycle ad/desorption stress test. The amino-modified compounds H2N-UiO-66 and H2N-MIL-125 feature high heat of adsorption (89.5 and 56.0 kJ mol(-1), respectively) and a very promising H2O adsorption isotherm due to their enhanced hydrophilicity. For H2N-MIL-125 the very steep rise of the H2O adsorption isotherm in the 0.1 < p/p0 < 0.2 region is especially beneficial for the intended heat pump application.

Hierarchical MOF-xerogel monolith composites from embedding MIL-100(Fe,Cr) and MIL-101(Cr) in resorcinol-formaldehyde xerogels for water adsorption applications

“…Water is the working fluid of choice because of its high evaporation enthalpy (2440 kJ·kg -1 at 25 °C) and non-toxicity despite the need to wor k under vacuum because of the low vapor pressure of only 3.17 kPa at 25 °C [15,25,26].…”

Tunable Water and CO2 Sorption Properties in Isostructural Azine-Based Covalent Organic Frameworks through Polarity Engineering

“…In recent years, metalorganic frameworks and porous carbons came into focus as potential water sorbents. [11][12][13][14][15] Besides initial experiments by Banerjee and co-workers, [16][17][18] COFs have not been investigated as potential water sorbents in detail so far. COFs have garnered significant attention owing to their tunable pore sizes and high porosity combined with their long-range ordered crystalline structure.…”

Co@NH2-MIL-125(Ti): cobaloxime-derived metal–organic framework-based composite for light-driven H2 production

“…NH 2 -MIL-125(Ti) was selected as host material because (i) the overall MOF structure is stable in aqueous media, 43,44 (ii) the multinuclear Ti-centers are both photo-and redox-active 24,45 and (iii) recent experimental 37 and theoretical studies 46 have shown that the photochemical properties can be tuned by changing the aromatic linker. It is noteworthy that NH 2 -MIL-125(Ti) has been used for photocatalytic hydrogen production, both in the absence and presence of Pt-nanoparticles, 24 suggesting that the reduction potential of the excited states in the MOF is sufficient to drive proton reduction in line with computational predictions.…”