Hierarchically porous ZIF-67/chitosan beads with high surface area and strengthened mechanical properties: Application to CO2 storage

In this work, zeolitic imidazolate framework-67 (ZIF-67)/chitosan composite beads were prepared by immersing chitosan beads incorporating cobalt (hydr)oxide into a solution containing the organic linker (2-methylimidazole). Compared to the conventional preparation protocols for metal-organic framework/polymer beads, the in-situ growth approach developed herein allows obtaining higher surface area with the shaped composites, up to 1200 m2/g for ZIF-67/CS2:1. The CO2 adsorption capacity of these ZIF-67/chitosan beads was investigated and reached 1.21 mmol/g at 273 K, which represents almost 100% of the adsorption capacity of pure ZIF-67, in line with the preserved surface area despite the incorporation of the 19% of additives included. Importantly, the ZIF-67/chitosan beads with an average bulk (crush) strength of 1.57 N could be easily regenerated, with a retained efficiency above 97% after 6 cycles. Furthermore, a possible mechanism for CO2 adsorption is discussed.