Modulated Growth of MOFs to Fabricate ZIF-8@Chitosan/Polyvinylpyrrolidone Hydrogels with Improved Adsorption Capacity for CO₂

Abstract

ZIF-8@chitosan (CS)/polyvinylpyrrolidone (PVP) hydrogels (CP x HGZ) were fabricated by in situ growth of metal− organic framework (MOF) crystals on the network of CS/PVP semiinterpenetrating hydrogels. The ZIF-8 crystals were assembled in the channel of hydrogel and coated by networks of hydrogel. Morphology and distribution of the ZIF-8 crystals in CS/PVP hydrogels were modulated by the polymer network of hydrogels. PVP played a key role in guiding the growth of ZIF-8 crystals and preventing aggregation of ZIF-8 crystals in the network of CS/PVP hydrogel. Additionally, the PVP content in hydrogels influencing the adsorption capacity of CP x HGZ for CO 2 was explored. With increasing PVP content in the hydrogels, the equilibrium adsorption of CP x HGZ for CO 2 was increased. Especially, the equilibrium adsorption of CP 10 HGZ for CO 2 was increased by 22%, which was higher than that of the pure ZIF-8 crystals. The results of kinetic simulation, XRD spectra, and FT-IR spectra revealed that the adsorption mechanism of CP x HGZ for CO 2 was mainly chemisorption. The presence of multisites, including the amine groups in CS and PVP as well as metals in ZIF-8, was beneficial for enhancing the adsorption capacity of CP x HGZ for CO 2 .