Size Controllable Synthesis of Zif-8 and Derived Nitrogen-Rich Porous Carbon for Co2 and Vocs Adsorption

It’s acknowledged that surface chemical and pore structure of adsorbent are main parameters to determine adsorption results. Herein, we reported a size controllable preparation of zeolitic imidazolate frameworks-8 (ZIF-8) with different average sizes (50, 120, and 2200 nm) and demonstrated their specific surface area and pore volume decreased with increasing particle size. ZIF-8 (ZN) exhibits a large specific surface area (1626.4 m2 g-1) and total pore volume (1.088 mL g-1), but it has been shown to lack the non-specific adsorption capacity for the adsorbate. Carbonization at 800 °C is proved to be an effective method to expose massive surface nitrogen-containing functional groups and adjust the aperture to an appropriate pore size range for derived porous carbon of ZIF-8 (ZCN). High nitrogen content (18.7 at %) greatly improves the affinity for CO2 and VOCs, as explained by the density functional theory (DFT) calculation results. Meanwhile, particle size influences the pore-forming results after carbonization directly. Among them, ZC50 generates a certain amount of narrow micropore in range of 0.7-1.0 nm, located in the optimal pore size range of CO2 adsorption calculated by GCMC, thus possessing the largest CO2 adsorption capacity (4.03 mmol g-1 at 25 ℃). Besides, ZC120 exhibits more superior mesopore structure that could provide mass transfer channel and strengthen multilayer adsorption for VOCs. This study provides an important hint for particle size effect on pore-forming after carbonization to improve corresponding adsorbate adsorption.