Tailored pore structure of ZIF-8/chitosan-derived carbonaceous adsorbent by introducing mesoporous silica nanoparticles for superior CO2 uptake

The shaped hierarchical porous carbon derived from ZIF-8, MSNs (mesoporous silica nanoparticles) and CS (chitosan) has been prepared by in situ assembly and post-annealing process. By tunning carbonization temperatures (from 450 to 650 °C), a series of CS/ZIF-8/MSNs carbonaceous millimetre-sized spheres with honeycomb internal structures and hierarchical pores have been developed for CO2 uptake. CS/ZIF-8/MSNs-525 (the sample treated at 525 °C) exhibited a higher CO2 capacity (1.32 mmol/g, 1 atm) than that of other samples due to its appropriate mesopores (∼11 nm), micropores (∼0.73 nm) and BET surface area (∼459.2 m2g−1). The XRD pattern of CS/ZIF-8/MSNs-525 suggested that MSNs would not affect sample structure, which performed largely maintained ZIF-8 diffraction. The SEM/EDS image of CS/ZIF-8/MSNs-525 showed that MSNs (∼50 nm) has been well decorated onto the surface of ZIF-8 by in situ assembly and carbonization, thus indicating a hierarchical structure formed. In addition, the TG-MS technology has been also utilized to clarify that MSNs assembly would not affect the carbonization process during the formation of CS/ZIF-8/MSNs-525. Moreover, the addition of MSNs facilitated a proper pore structure and higher CO2 capacity of CS/ZIF-8/MSNs-525 compared with that of CS/ZIF-8 carbon spheres (0.9 mmol/g, 1 atm). Particularly, the CS/ZIF-8/MSNs-525 exhibited excellent stability and recyclable performance after CO2 adsorption in 10 adsorption-desorption cycles. This MSNs assembly strategy could induce a simple way for obtaining novel shaped carbonaceous adsorbent for superior CO2 uptake in industrial fields.