Metal-organic Frameworks (MOFs) are crystalline porous materials that have been widely investigated for use in catalysis, gas storage and separation. They are typically synthesised as microcrystalline powders, however, this results in reduced packing density and handling challenges.[1] To overcome these limitations, the microcrystalline powder can be converted into or synthesised as a monolithic structure whilst retaining or enhancing the beneficial properties of the MOF.[2] One promising method of structuralising MOFs into monolithic materials involves the conversion of porous inorganic templating materials. Additionally, as MOFs are typically microporous, utilising sacrificial templating materials with macro/meso porosity can generate hierarchical porosity.[3,4]
Herein, we report the synthesis of hierarchically porous monolithic Al-MOF materials derived from sacrificial Al-gel based templates. Leveraging a prior report,[3] we show the versatility of the approach with a range of Al-MOFs (MIL-53, MIL96, DUT-5, MOF-253) able to be derived from a macroporous Al sol-gel template under solvothermal conditions. The synthetic parameters affecting conversion (reaction time, solvent mixture) were investigated, allowing for control over both the extent of MOF formation and the ratio of macro- and microporosity. Modification of synthetic conditions also allowed for control over MOF phase, with synthesis conditions able to be tuned to form mesoporous MIL-110 or microporous MIL-96 MOF phases.