Cross-coupling reactions are a fundamental tool in the large scale synthesis of pharma-, agro- and fine chemicals. Homogeneous palladium complexes remain the state-of-the-art catalysts even though the use of heterogeneous...

We report the effect of inorganic and organic acids and bases, in combination with different solvents, on the crystallinity and porosity of defective UiO-66 MOFs.

UiO-66 is one of the most chemically stable Metal-organic frameworks (MOFs) available. However, little is known about its stability in organic solvents. In this study, we synthesized a highly defective UiO-66 (HD-UiO-66) and explored how its textural properties change when exposed to weak and strong acids, both organic and inorganic in nature, and dissolved in different solvents, water, dichloromethane (DCM), and tetrahydrofuran (THF). Exposing defective UiO-66 to weak acids and bases, such as acetic acid and triethylamine, maintains its crystalline structure and porosity, irrespective of the solvent. Sulphuric acid decomposes HD-UiO-66 in organic solvents but not in water, trifluoroacetic acid decomposes the framework only in DCM. Tetramethylguanidine decomposes HD-UiO-66 in organic solvents but mantains some of the MOFs porosity and crystalline structure in water, whereas potassium carbonate damages the MOF to a greater extent in water than in organic solvents. Our results show that the acid/base properties of the solvent modulate the strength of acids and bases and its polarity determines the extent of their solvation, thus playing a crucial role in altering the MOF’s textural properties. This systematic investigation highlights the central role played by the solvent in tuning the stability of MOFs, which is relevant for liquid-phase applications in acidic and basic environments, such as catalysis and adsorption.

UiO-66 is one of the most chemically stable Metal-organic frameworks (MOFs) available. However, little is known about its stability in organic solvents. In this study, we synthesized a highly defective UiO-66 (HD-UiO-66) and explored how its textural properties change when exposed to weak and strong acids, both organic and inorganic in nature, and dissolved in different solvents, water, dichloromethane (DCM), and tetrahydrofuran (THF). Exposing defective UiO-66 to weak acids and bases, such as acetic acid and triethylamine, maintains its crystalline structure and porosity, irrespective of the solvent. Sulphuric acid decomposes HD-UiO-66 in organic solvents but not in water, trifluoroacetic acid decomposes the framework only in DCM. Tetramethylguanidine decomposes HD-UiO-66 in organic solvents but mantains some of the MOFs porosity and crystalline structure in water, whereas potassium carbonate damages the MOF to a greater extent in water than in organic solvents. Our results show that the acid/base properties of the solvent modulate the strength of acids and bases and its polarity determines the extent of their solvation, thus playing a crucial role in altering the MOF’s textural properties. This systematic investigation highlights the central role played by the solvent in tuning the stability of MOFs, which is relevant for liquid-phase applications in acidic and basic environments, such as catalysis and adsorption.