In-situ SIFSIX-3-Cu growth into melamine formaldehyde sponge monolith for CO₂ efficient capture

CO₂ adsorption separation by metal-organic frameworks (MOFs) is an efficient carbon capture and storage method. We proposed a strategy of two-step in-situ MOFs growth in porous carrier to prepare high efficient CO₂ adsorbent for low concentration CO₂ adsorption. At first, metal ions were introduced into the pores of melamine formaldehyde sponge (MFS) monolith carriers onto which inner walls a thin layer of PVA was adhered in advance, then organic ligands were introduced into the pores of MFS. The thin PVA layer greatly strengthened the anchoring of MOFs in the carriers. The in-situ MOFs growth in MFS effectively avoided crystals stack together, presented a multi-level pore structure in fixed bed, which is beneficial for gas diffusion with rapid adsorption kinetics. The CO₂ adsorption was carried out in a fixed bed by conducting breakthrough experiments. The MOFs crystals uniformly grown in pores of MFS. The monolith composite adsorbent prepared at 6% organic ligand, with MOFs loading ratio of 5 g·g⁻¹(carrier), showed good CO₂ uptake value of 1.02 mmol·g⁻¹(adsorbent) in the CO₂/N₂ atmosphere with CO₂ concentration of 5000 PPM at 20 °C. By secondary growth, higher MOFs loading ratio and desired morphology crystals were achieved. The effects of CO₂ concentration and gas flow rate on adsorption properties of the secondary-growth adsorbent were investigated. The working CO₂ capacity was better than that of 13X zeolite. The presence of 21 vol% O₂ did not influence the CO₂ adsorption. After 10 cycles adsorption-desorption in 15 days, the as-prepared adsorbent still showed a very stable adsorption separation performance.