Enhanced non-linear optical properties of porphyrin-based polymers covalently functionalized with graphite phase carbon nitride.

In our work, a flurry of original porphyrin-based polymers covalently functionalized g-CN nanohybrids were constructed and nominated as PPorx-g-CN (x = 1, 2 and 3) through click chemistry between porphyrin-based polymers with alkyne end-groups [(PPorx-C≡CH (x = 1, 2 and 3)] and azide-functionalized graphitic carbon nitride (g-CN-N). Due to the photoinduced electron transfer (PET) between porphyrin-based polymers [PPorx (x = 1, 2 and 3)] group and graphite phase carbon nitride (g-CN) group in PPorx-g-CN nanohybrids, the PPorx-g-CN nanohybrids exhibited better non-linear optical (NLO) performance than the corresponding PPorx-C≡CH and g-CN-N. It found that the imaginary third-order susceptibility ( [χ]) value of the nanohybrids with different molecular weight (MW) of the Porx group in the nanohybrids ranged from 2.5×10 to 7.0 × 10 g mol was disparate. Quite interestingly, the [χ] value of the nanohybrid with a Porx group's MW of 4.2 × 10 g mol (PPor2-g-CN) was 1.47 × 10 esu, which exhibited the best NLO performance in methyl methacrylate (MMA) of all nanohybrids. The PPorx-g-CN was dispersed in polymethyl methacrylate (PMMA) to prepare the composites PPorx-g-CN/PMMA since PMMA was widely used as an alternative to glass. PPor2-g-CN/PMMA showed the excellent NLO performance of all nanohybrids with the [χ] value of 2.36 × 10 esu, limiting threshold of 1.71 J/cm, minimum transmittance of 8% and dynamic range of 1.09 in PMMA, respectively. It suggested that PPorx-g-CN nanohybrids were potential outstanding NLO materials.