Assisting the carbonization of biowaste with potassium formate to fabricate oxygen-doped porous biochar sorbents for removing organic pollutant from aqueous solution

•OPBs were synthesized by the assisted-pyrolysis of biowaste with potassium formate.•O content (26%) and surface functional groups were abundant in OPBs.•Pore structure with high specific surface area (1386 m2 g−1) was formed in OPBs.•OPBs showed enhanced sorption capacity for DEP (453 mg g−1).•Pore filling, π-π stacking and H bonding dominated the DEP sorption by OPBs.