Mustard gas and other chemical warfare agents (CWAs) are a global threat to public security, arising from unpredictable emergencies and chemical spill accidents. So far, photocatalysts such as metal clusters, polyoxometalates and porous solids have been exploited for oxidative degradation of mustard gas, commonly with ¹O₂ as reactive species. However, the production of ¹O₂ is oxygen-dependent and requires a high oxygen concentration to sustain the detoxication process. For safety and operation process considerations, it is always preferable to rapidly detoxify dangerous chemicals in the atmosphere of room air. In this work, a porous aromatic framework, PAF-68, was synthesized as a metal-free photocatalyst. In the presence of PAF-68, fast detoxication occurred in typical room air atmosphere. The half-life (t_1/2) for the complete conversion of mustard gas simulant to nontoxic product in room air was only 1.7 min, which is comparable to the performance in pure oxygen, surpassing that of any other porous photocatalysts. It was found that ˙O₂⁻ rather than ¹O₂ is the predominant reactive species initiated by PAF-68 for mustard gas detoxication. Unlike the formation of ¹O₂ which prefers the environment of pure oxygen, generation of the ˙O₂⁻ is an oxygen-independent process. It is suggested that amorphous PAFs possess low exciton binding energy and long decay lifetime, which facilitate the generation of ˙O₂⁻, and this offers a general design strategy to detoxifying chemical warfare agents under real-world conditions.