A case study for an eco-design of aluminum terephthalate metal-organic framework- MIL-53(Al) for CO2 and methane adsorption

Metal-organic frameworks (MOFs) are highly promising materials for environmental applications, including gas separation and CO2 capture. In the present study, a detailed comparison was first done on the hydrothermal production of MOF with terephthalic acid and aluminum- MIL-53(Al), synthesized with 24 h, 48 h, and 72 h time reaction. A comparative characterization between the different MIL-53(Al) syntheses was done by X-Ray Diffraction, scanning electron microscopy (SEM), thermogravimetric and infrared analysis, XPS spectroscopy, 13C MAS NMR and 27Al MAS NMR and CO2 Drifts, showing the maintenance of the structure and coordination environment for the 24 h synthesis. MIL-53(Al) synthesized at 24 h presented a very good surface area of 1711 m2 g−1 and adsorbed up to 13 mmol/g of CO2 and 4 mmol/g of CH4 at 25 bar and 348 K. Life cycle assessment (LCA) was first done to compare hydrothermal 72- and 24 h-MIL-53(Al), showing a reduction in electricity of 66.7%, and for freshwater ecotoxicity and ozone depletion, despite the great environmental burden of the solvents employed in the activation step. A greater reduction in environmental impacts was observed with the proposal of a method for 24 h-MIL-53(Al) synthesis which includes the aluminum recovery, the reduction of reaction time and volume of solvents, mainly observed for metal depletion, freshwater ecotoxicity, particulate matter formation, climate change, and human ecotoxicity, with reductions of 77.1%, 70.38%, 65%, 44.7% and 43.3%, respectively.