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 (GPDZxAG, where x 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.