Encouraged by the above findings, we further explored the application potential of PDA-MAH for disinfection in air decontamination using the face mask as a model. By coating the PDA-MAH photocatalysts on the middle layer of the face mask, the antibacterial performance of the PDA-MAH coated mask was compared with that of a commercial mask (N95). As a proof of concept, a semi-closed system reactor was built in which a mask was used to divide the reactor chamber into two separate parts (Figure ). After flowing bioaerosols from the inlet, through the mask, and over the remaining reactor chamber, the exhaust air stream was exposed to the bacterial collectors at the exit of the reactor, and the number of bacteria surviving on the collector plates was counted. As shown in Figure , PDA-MAH mask showed >99% E. coli inactivation in 60 min under visible light irradiation, which is greatly superior to the commercial mask (N95) under visible light (<96%) and PDA-MAH mask in dark (<94%) over the same time period. Helium ion microscope provided more intuitive evidence for the demonstration experiment above (Figure ). Residual bacteria attached to the PDA-MAH mask were observed after the dark reaction experiment but seldom found after the visible light irradiation with photocatalysis. In addition, repeated experiments showed that the PDA-MAH mask still maintained sufficient activity after four runs, suggesting the high stability of PDA-MAH for air sterilization (Figure ). The remarkable bactericidal activity thus attested to the great protective coating function of PDA-MAH. In conclusion, we proposed and validated a new strategy for accelerating the CST process of polymeric bulk photocatalysts through breaking lattice symmetry in highly crystallized PPI nanosheets. By using this strategy, a highly efficient photocatalyst PDA-MAH was synthesized facilely from the fine chemicals intermediates p-phenylenediamine and mphthalaldehyde. PDA-MAH showed strong internal electric field, fast CST process, and a prominent photocatalytic disinfection performance under visible lights irradiation that surpassed the best of the previously reported polymeric photocatalysts. Importantly, this work highlights the significance of lattice symmetry control in polymeric photocatalysts for regulating the CST process and boosting the photocatalytic activity, and provides a new way for polymer semiconductor designs besides modifying polymer chemical structures.