Utilizing sunlight as a renewable energy source, photocatalytic technology is a promising approach to addressing a number of the energy and environmental problems that the world faces today. Recently, polymeric photocatalysts have attracted much attention because of their fascinating properties, such as tunable electronic structures, environment benignity and low-cost processability, etc. However, the poor charge separation and transport (CST) process has undermined photocatalytic efficiency in most polymeric photocatalysts. One way to gain an additional driving force for the CST process in polymers is the introduction of donor-acceptor (D-A) moieties. Once properly designed, the D-A moieties with dipole moments can generate the local internal electric field (IEF), which facilitates the separation of photogenerated charges via intramolecular charge transfer. However, building D-A moieties with high dipole moments often requires elaborate design and complex synthesis, thus limiting the large-scale application of this approach. Moreover, the highly dipolar D-A moieties tend to remain in anti-parallel arrangement, which is unfavourable for the generation of distinct dipole moments in the polymer bulk, resulting in weak CST process throughout the material. Therefore, it's highly desired to find a suitable strategy that can increase the dipole moments and, hence, strengthen the IEF over the long range throughout whole bulk, in order to improve the efficiency of the CST process and the related photocatalytic performance in polymeric photocatalysts. Inspired by the lattice distortion strategy, which was shown to be highly effective in enhancing IEF in the bulk TiO2 and BiPO4 system, the present study applied a similar lattice symmetry-breaking strategy on the typical crystalline conjugated polymers, poly-(phenylene-imine) (PPI). These facile-to-prepare PPIs from the intermediates of fine chemicals (phenylenediamine and phthalaldehyde) possess identical functional groups, weak D-A moieties, and quite different lattice symmetries. As shown in Scheme 1, when the lattice symmetry was broken deliberately, the elimination of symmetric centre would introduce non-overlap positive and negative charge centres, creating dipole moments in the lattice. Therefore, a remarkable IEF would be built up along the dipole direction throughout the whole bulk. In this work, we verified the feasibility of the hypothesis above by demonstrating that PDA-MAH, which had crystallized in monoclinic structure without lattice symmetry centre, yielded a much stronger IEF than the orthorhombic PDA-PAH and the amorphous MDA-MAH. The robust IEF of PDA-MAH greatly accelerated the CST process, leading to a rapid visible-light-driven water disinfection with 7 logs (>99.9999%) inactivation of E. coli within 1 h, which is the highest among those with previously reported polymeric photocatalysts. The PPIs were synthesized via acetic acid catalyzed Schiff base reaction in the mixed solvents (see Supporting Information). p-/m-phenylenediamine (PDA/MDA) and p-/mphthalaldehyde (PAH/MAH) were selected as the monomers to build the PPIs, and three copolymers were referred to as PDA-PAH, PDA-MAH, and MDA-MAH, respectively (Figure ). As shown in the Fourier transform infrared (FTIR) spectra (Figure ), the identical bands of the three PPIs samples at 1640 cm -1 clearly demonstrated that the imine (C=N) bonds had formed by the Schiff-base condensation. The formation of C=N bonds was further confirmed by X-ray photoelectron spectroscopy (XPS) as N1s peaked at around 398.8 eV in all the spectra (Figure and). The resonances during 100-160 ppm in 13 C cross-polarization (CP) magic-angle spinning (MAS) NMR spectra corresponded to the C atoms on the benzene rings from the phthalaldehyde and phenylenediamine moieties (Figure ), confirming the substitution relationships on the benzene ring of the respective three PPIs. Noting that the resonances at around 150 ppm were attributed to the C atoms in the imine groups. To distinguish the bulk phase structures, three PPIs were characterized by powder X-ray diffraction (PXRD). Both PDA-PAH and PDA-MAH were highly crystalline while MDA-MAH was amorphous (Figure ). Le Bail fitting of the PXRD patterns of PDA-PAH and PDA-MAH, shown in Figure and 1b, indicated that PDA-PAH had an orthorhombic structure with unit cell parameters of a = 22.915 Å, b = 10.746 Å, c = 7.578 Å, (space group: Pmcm) and PDA-MAH assumed a monoclinic structure with lattice parameters of a = 10.666 Å, b = 10.912 Å, c = 7.051 Å, and β = 96.200 o (space group: Pm). The symmetry breaking at the lattice level from the orthorhombic to the monoclinic structure eliminates the symmetric center in the unit cell, hence, creating dipole moments in the lattice. Apparently, the symmetry reduction of the monomers may have led to the lattice symmetry breaking of the bulk phase crystals. Under the transmission electron microscope (TEM), the crystallized PPIs (i.e. PDA-MAH and PDA-PAH) adopted typical 2D nanosheet morphology (Figure , 1d); the atomic force microscopy showed ~4.5 nm thickness for the same two PPIs nanosheets (Figure ). Hence, two crystallized PPIs have similar chemical structure and morphology, and their primary difference lies at the centrosymmetry due to symmetry breaking at the lattice level. To investigate the buildup of IEF following the symmetry breaking, the surface charge density and the Zeta potential were measured in three PPI samples by the Kelvin probe force microscope (KPFM) and from the electrophoretic mobility, as both were recently used as the descriptors of the IEF. As shown in Figure (S8), PDA-MAH exhibited the highest surface potential (ΔE = 205 mV) among three PPIs, five times than that of PDA-PAH (40 mV). The Zeta potentials of three PPIs followed the same trend as the KPFM surface potential (Figure ), with the highest Zeta potential found in PDA-MAH. Thus, we can conclude that the PDA-MAH had the most robust IEF. Since PDA-MAH and PDA-PAH both were well crystallized, the difference in the IEF of those two samples would be mainly caused by the symmetry reduction in crystal structures, as their oligomer dipoles were similar (Figure ). Since the irregular chain arrangement counteracted the monomer dipole, the amorphous MDA-MAH demonstrated remarkably weaker IEF. The much stronger IEF in PDA-MAH is expected to add significant driving force in the CST process for the photocatalyst. Aside from the CST process, photocatalytic activity also depends on the photon absorption process. However, ultraviolet diffuse reflectance spectra (UV-DRS, Figure ) showed the close absorbance stopping edges of three PPIs prepared here, indicating similar light absorption at visible wavelengths. The appreciable visible light harvest ability and appropriate band structures (Figure , concluded from UV-DRS spectra, XPS valence band spectra in Figure , and Mott-Schottky curves in Figure ) pointed to the possible photocatalytic capability of the PPIs thermodynamically, while the major differences in the kinetic process, especially the CST process, were observed as presented below. First, photoluminescence spectra (Figure ) demonstrated that PDA-MAH had the lowest recombination of photoexcited electron-hole pairs. Second, transient fluorescence spectroscopy revealed that the transient fluorescence lifetime of PDA-MAH was longer than those of the other two PPIs, as an indication that the robust IEF in PAD-MAH had enhanced the separation and migration rate of the photogenerated charge carriers (Figure ). Thirdly, electrochemical impedance spectroscopy (EIS) showed that PDA-MAH had a much smaller semicircular Nyquist plot radius than other PPIs, especially under light illumination (Figure ), suggesting a lower charge transfer resistance in PDA-MAH bulk. Fourthly, the strong transient photocurrent response of PDA-MAH provided further evidence that the robust IEF of PDA-MAH accelerated the CST process in the bulk (Figure ), which could boost photocatalytic performance in the kinetic aspect. The photocatalytic activities of the as-synthesized PPI samples were then evaluated by their photocatalytic disinfection performance under visible light illumination. Using E. coli as the target indicators, the kinetics of the photocatalytic antibacterial activity of PPI samples were examined in terms of the bacterial survival ratio as a function of the photocatalytic treatment time. As shown in Figure , PDA-MAH under visible light exhibited over 99.99999% E. coli inactivation in just 1 hour, whereas PDA-PAH acted very slowly at a rate of about 99% disinfection efficiency after 120 min; and the MDA-MAH showed negligible toxic effect on E. coli over the same time period. For reference, comparison experiments demonstrated that visible light irradiation alone caused no photolysis in E. coli and all of the PPI samples had no toxic effect on bacterial cells without the light illumination. Obviously, the strong IEF in PDA-MAH had boosted photocatalytic activity vastly. More strikingly, we found that PDA-MAH exhibited the best catalytic bacterial disinfection rate under visible light irradiation as compared with those of reported metal-free photocatalysts (Figure and Table ), indicating its great potential in future applications in water treatment practice. Given the superior disinfection performance of PDA-MAH, the photocatalytic mechanism was further studied. Reactive species (RS) quenching experiments demonstrated that H2O2 generated in situ during the photocatalytic process played the dominant role in bacterial inactivation among all the RSs (Figure ) since the addition of the H2O2 scavengers significantly reduced the photocatalytic disinfection rate. When the concentration of in situ formed H2O2 was measured over time, the H2O2 concentration initially increased with light exposure time, then became relatively stable (ca. 6 μM) with prolonged illumination time (Figure ), which is congruent with the process where the H2O2 is continuously produced and consumed dynamically. Furthermore, rotating disk electrode (RDE) studies revealed that the H2O2 on PDA-MAH was generated through the two-electron oxygen reduction pathway (Figure , S19). To gain more insight into the 2e -oxygen reduction pathway at the molecular level, density functional theory (DFT) calculations were performed to determine the thermodynamic energy for the critical step in H2O2 production. Since recent studies have identified that the O2 adsorption and generation of endoperoxide species is the critical step to reduce O2 into H2O2 on polymeric photocatalyst, we compared the energies of formation of O2* on the four different active sites. The calculations showed that the endoperoxide species had favorable Gibbs free energies when anilino or imine (C=N) moieties acted as the O2 adsorption sites (Figure ). The calculations further confirmed both the energies of formation of O2* and OOH* on the imine site were much smaller than that on aniline, suggesting that imines tend to be the active site of the two-electron reduction pathway (Figure ). Based on the above analysis, the selective H2O2 formation mechanism on the photoactive PDA-MAH is depicted in Figure , where the molecular O2 was first spontaneously adsorbed on the imine site to produce endoperoxide species, and the endoperoxide species then reacted with 2e -and H + to form OOH* species. Subsequent protonation of the OOH* species finally produced H2O2 and completed the photocatalytic cycle.