The state-of-the-art approaches for adjusting the structural characteristics of porous carbons are the aftertreatments

which are complicated and time consuming. In this work

a facile approach was developed

i.e.

controlling the initial oxygen concentration in-situ during the direct carbonization of zeolitic imidazole framework-8 (ZIF-8)

to adjust the pore structure and prepare hierarchically porous carbons. The introduction of oxygen can significantly affect the crystalline and pore structures of porous carbons

and promote the pore widening and the formation of mesopores. An appropriate initial oxygen concentration can notably enhance the surface area and mesopore volume of porous carbon

and then improve the adsorption capacity toward methylene blue (MB) dye from water by 3.4 times. The developed approach is more efficient at lower carbonization temperature. Moreover

the introduction of oxygen can increase the ratio of HO-C=O groups on the carbon surface

leading to enhanced interaction with MB molecules and higher adsorption capacity toward MB. The as-prepared porous carbons exhibit superior adsorption capacities toward MB dye as compared to the reported ZIF-8 derived carbons. These findings would aid the development of porous carbon materials with high performance.