## 2 Results and Discussion
### Photocatalytic Performance of TiO\({}_{2}\), TC and PPTC  
The photocatalytic degradation rates of DMF catalyzed by TiO\({}_{2}\), TC, and PPTC under simulated sunlight irradiation for different duration (0.5-3.0 h) are shown in Figure 6. It can be seen that TiO\({}_{2}\), TC, and PPTC as the photocatalysts all can catalyze the photocatalytic degradation of DMF under simulated sunlight irradiation, and the degradation rate of DMF gradually increases with increasing irradiation time thereunder. Particularly, after 3 h of illumination in the presence of PPTC, TC, and TiO\({}_{2}\), the tested DMF is degraded by a rate of 73.7%, 65.4%, and 52.8%, respectively. This demonstrates that the as-prepared PPTC photocatalyst possesses excellent photocatalytic degradation efficiency toward DMF. Usually, the photocatalytic performance of photocatalyst is highly dependent on its specific surface area and the recombination rate of its holes and photo-excited electrons [20]. It has been found that the enhancement in the adsorption capacity of photocatalysts contributes to increasing photocatalytic efficiency [7; 11]. As listed in Table 1, PPTC has the largest specific surface area (whether by the  
Figure 5: UV-vis absorbance spectra of TiO\({}_{2}\), TC, and PPTC. Figure 6: Photocatalytic performance of TiO\({}_{2}\), TC, and PPTC toward degradation of \(N\),\(N\)-dimethylformamide (DMF). BET (Brunauer, Emmett, and Teller) multi-point-contact method or by Langmuir single-point-contact method) as well as the maximum total pore volume of single-point adsorption among the three tested photocatalysts, which is why it exhibits better photocatalytic performance than TiO\({}_{2}\) and TC toward the degradation of DMF [20; 21]. In other words, as compared with TiO\({}_{2}\) and TC, PPTC with larger specific surface area and total pore volume as well as smaller average pore size would have more opportunities to contact and adsorb DMF, thereby achieving enhanced photocatalytic degradation of the organic pollutant [21; 22]. In the meantime, as shown in Figure 7, TiO\({}_{2}\) has the strongest emission intensity while PPTC has the lowest one. This reveals that PPTC has a low hole-electron recombination rate, which corresponds well to its enhanced photocatalytic degradation ability for DMF [21]. The recyclability of TiO\({}_{2}\), TC, and PPTC toward the photocatalytic degradation of DMF is shown in Figure 8. TiO\({}_{2}\) and TC can be reused four times and five times, respectively. Photocatalyst PPTC, however, is still able to degrade DMF even after six cycles of reuse. There is obvious difference in the three photocatalysts that PPTC can be reused more times in photocatalytic degradation of DMF. This could be because the TiO\({}_{2}\)/Cu composite is embedded well in the pores of the porous polymer and prevented from loss upon exposing to simulated or natural sunlight irradiation, thereby leading to improved recyclability of PPTC than TiO\({}_{2}\) and TC [22]. Regrettably, PPTC only has about 20% degradation rate after five times of reuse, the main reason may be attributed to organic pollutants covering the pore of photocatalysts [23]. In addition, the little leaching of metallic Cu also affects the activity of photocatalysts. Table 2 lists the photocatalytic degradation rate of DMF catalyzed by TiO\({}_{2}\), TC, and PPTC without illumination (in the dark) and under the irradiation of simulated (Xe lamp) or real sunlight. Without illumination, the degradation rate of DMF is very low even under the catalysis by PPTC, possibly due to highly retarded adsorption of DMF thereunder. Besides, whether under simulated sunlight or nature sunlight irradiation, the degradation rate of DMF catalyzed by PPTC is the maximum (73.7% and 64.0%), which indicates that PPTC could have good prospects for the photocatalytic degradation of organic pollutants like DMF, methyl orange, methylene blue, phenol, and other organic pollutants.