In this study, we develops a one-step and scalable approach to synthesize functional carbons with a tuneable and hierarchically porous structure as well as tailored surface chemistry for environmental applications in CO2 adsorption and carbocatalysis to remove emerging water contaminants. By pyrolyzing a mixture of wheat flour and NaHCO3/Na2CO3/K2CO3 at 700 degrees C, honeycomb structured carbons (700-PC) with dominant micropores can be formed and exhibit an excellent CO2 storage capacity of 6.8 mmol g(-1) at 0 degrees C and ambient pressure. By including dicyandiamide in the precursors, coralloid carbon skeletons in a micro-and meso-porous texture are selectively formed in the N-doped hierarchical porous carbons (N-PCs). 800-N-PC (N-PCs prepared at 800 degrees C) with a high surface area of 3041m(2) g(-1) shows an enhanced capacity of 19.4 mmol g(-1) at 0 degrees C, 10 bar. For water remediation, 800-N-PC exhibits the most efficient degradation of p-hydroxybenzoic acid (HBA) by advanced oxidation processes (AOPs), with a high reaction rate constant of 0.39 min(-1) at 25 degrees C. In addition, 800-N-PC shows selective adsorption of HBA in a mixed solution of HBA and phenol, while both of them can be effectively degraded by the AOPs. The mechanism of adsorption and catalysis of the newly developed porous carbon is discussed.