Regular Growth of MOFs Crystals in Restricted Networks to Prepare Chitosan/Polyvinylpyrrolidone/ZIF-8 Gel Beads for Adsorb CO2

Abstract

Chitosan (CS) and polyvinylpyrrolidone (PVP) were crosslinked by glutaraldehyde and Zn2+ to fabricate polymer networks. Subsequently, CS/PVP sols were dropped into an alkaline solution resulting in deionization of hydrophilic groups and contraction of polymer networks to form CS/PVP beads with restricted networks. ZIF-8 crystals were incubated in the restricted networks to prepare ZIF-8@CS/PVP gel beads (CPZxB). The growth of ZIF-8 crystals in the restricted networks had more regular morphology. Meanwhile, the size of ZIF-8 crystals in beads were modulated by the molar ratio of 2-MeIM to Zn²⁺. Specifically, the size of ZIF-8 crystals was decreased with increasing the ratio of 2-MeIM to Zn2+. Additionally, the equilibrium adsorption capacity of beads for CO2 was 3.13 mmol/g oud initial pressure of 400kPa at 288.15K, and increased by 23% compared to ZIF-8 crystals. Adsorption mechanism was explored by kinetic model and Langmuir model, and the adsorption thermodynamic parameters were calculated using the Van't Hoff equation. The results indicated that adsorption of gel beads for CO2 primarily depended on chemisorption, and was a spontaneous exothermic process. As a result, it may be an effective strategy that growth of MOFs crystals in the confined networks could be form more regular morphology.