In Situ Growth of ZIF-67 Crystals in Networks Consisting of Graphene Oxide and Polydopamine to Fabricate Aerogels with Effective Absorption for Carbon Dioxide

Graphene oxide (GO)/polydopamine (PDA) hydrogels (GPDH) were sequentially immersed in a methanol solution of Co(NO₃)₂·6H₂O and 2-MIM to prepare GO/PDA/ZIF-67 aerogels (GPDZ_<i>x</i>AG, where <i>x</i> represents the molar ratio of 2-MIM to Co²⁺). The hierarchical structure consisting of GO/PDA networks and ZIF-67 crystals was established in the resulting aerogels, and the ZIF-67 crystals with a regular morphology were not aggregated obviously. The size of ZIF-67 crystals in aerogels was modulated by the molar ratio of the ligand to metal ion. The ZIF-67 crystallite size, calculated by the Williamson-Hall equation, decreased with an increase in the concentration of 2-MIM. Additionally, the aerogels exhibited effective absorption capacity for CO₂, and the equilibrium capacity of GPDZ₃₂AG for CO₂ was 5.04 mmol/g under an initial pressure of 400 kPa at 298.15 K. Compared with those of ZIF-67 and GO/PDA aerogel, the equilibrium adsorption capacity of GPDZ₃₂AG for CO₂ was increased by 133% and 83%, respectively. After five adsorption cycles, GPDZ₃₂AG maintained 85% of its initial efficiency. The adsorption mechanism was explored by the kinetic model and Langmuir model. The results indicated that absorption of aerogels for CO₂ was primarily dependent on chemical processes and fitted the Langmuir model.