BACKGROUND 2‐nitro‐4‐methylsulfonylbenzoic acid (NMSBA) is commercially produced from the oxidation of 2‐nitro‐4‐methylsulfonyltoluene (NMST) with nitric acid as oxidant and V2O5 as catalyst in a strong acid solution; this process suffers from the following shortcomings: the discharge of large amounts of wastewater and waste gas, as along with the generation of polynitro compounds. It is necessary to develop a technology to avoid the pollution caused by oxidizing NMST with nitric acid. NMSBA can be synthesized by oxidizing NMST with air under the catalysis of the porous carbon made from coconut shell with ZnCl2 as an activator together with Co/Mn/Br. RESULTS The optimum conditions for the preparation of the porous carbon are as follows: impregnation temperature 60 °C, ZnCl2 concentration 0.50 mol L−1, impregnation duration 6 h, carbonization temperature 600 °C, and carbonization time 4 h. The surface characterization suggests that the carbon made in this study holds smaller surface area, acidic groups, and basic groups than the commercial carbon but owns more carboxyl. CONCLUSION The Co/Mn/Br/AC (AC,the porous carbon made in this study) catalytic system is superior to the Co/Mn/Br/H3PMo12O40@CAC(CAC,commercial activated carbon) catalytic system in the production of NMSBA from the oxidation of NMST. The NMSBA selectivity gained by the former is 93.40%, while that gained by the latter is 87.14%. The former can cut down the consumption of NMST and the expenditure of catalysts. The catalytic ability of the AC catalyst relies on its surface chemical characteristics and physical properties. More carboxyl on AC is the reason for the upgrade of NMSBA selectivity. © 2022 Society of Chemical Industry (SCI).