CO2 capture using monolithic MOFs

https://doi.org/10.1039/D1FD00017A

“To investigate the bulk density properties of the synthesised materials, we performed Hg porosimetry on the monolithic and powdered MOF materials (Table 1). We have shown previously that _monoMOFs display higher bulk densities than powders and pelletised materials due to the exceptional control and close packing of the primary particles (i.e. crystallites) during the sol–gel synthesis. In turn, this leads to materials that maintain their porosity and performances and overcomes the limitations of traditional shaping techniques (i.e. pore collapse or low density due to high or low pressure, respectively, during the compression or pore blockage due to the use of binders). The bulk densities observed for _monoHKUST-1 (ρ_bulk = 1.06 g cm⁻³), _monoUiO-66 (ρ_bulk = 1.05 g cm⁻³), and _monoUiO-66-NH₂ (ρ_bulk = 1.25 g cm⁻³) were comparable to previous reports.^57,58 In contrast, the bulk densities of the powdered materials were significantly lower for HKUST-1 (ρ_bulk = 0.5 g cm⁻³), UiO-66 (ρ_bulk = 0.56 g cm⁻³) and UiO-66-NH₂ (ρ_bulk = 0.66 g cm⁻³). The lower density can be attributed to the poor packing, leading to large amounts of void space in the powder samples. When the bulk density is taken into account to calculate the volumetric BET area and volumetric total pore volume of each material (Table 1), the monolithic materials display significantly higher values compared to the powdered variants. In terms of performance, the monolithic materials display volumetric BET areas which are 79%, 48% and 150% higher for HKUST-1, UiO-66 and UiO-66-NH₂, respectively, compared to their powdered variants.”