Bare α-Bi2O3 known as poor photocatalyst was discovered as a terrific MW catalyst.
The MCOD process can efficiently degrade PNP and TOC without adding extra oxidants.
OH generated by MW excited holes acts as primary oxidant in the MCOD process.
The fluorescent probe technique was applied to confirm the existence of OH.
A possible catalytic mechanism of MCOD process over bare α-Bi2O3 was revealed.