Aluminum formate, Al(HCOO)₃: An earth-abundant, scalable, and highly selective material for CO₂ capture

A combination of gas adsorption and gas breakthrough measurements show that the metal-organic framework, Al(HCOO)₃ (ALF), which can be made inexpensively from commodity chemicals, exhibits excellent CO₂ adsorption capacities and outstanding CO₂/N₂ selectivity that enable it to remove CO₂ from dried CO₂-containing gas streams at elevated temperatures (323 kelvin). Notably, ALF is scalable, readily pelletized, stable to SO₂ and NO, and simple to regenerate. Density functional theory calculations and in situ neutron diffraction studies reveal that the preferential adsorption of CO₂ is a size-selective separation that depends on the subtle difference between the kinetic diameters of CO₂ and N₂. The findings are supported by additional measurements, including Fourier transform infrared spectroscopy, thermogravimetric analysis, and variable temperature powder and single-crystal x-ray diffraction.