Synthesis of porphyrin-based conjugated microporous polymers and investigation of nonlinear optical properties

Porphyrins, as planar macrocyclic compounds with 18π electrons, hold broad application prospects in the field of nonlinear optics. However, their strong self-aggregation properties cause a decrease in nonlinear optics, resulting in limited applications. To overcome this, two D–π–A type conjugated microporous polymers (ZnTFcPP-CMP and ZnTPyPP-CMP) were synthesized via Sonogashira–Hagihara coupling, utilizing ferrocene (Fc) or pyridine (Py) as donors and porphyrins as acceptors. Z-scan measurements (at 50 μJ in DMF) demonstrated that both CMPs exhibit significantly enhanced third-order NLO properties compared to pristine ZnTBrPP. Specifically, ZnTFcPP-CMP achieved a nonlinear absorption coefficient ( β ) of 1.60 × 10 −9  m/W and an imaginary susceptibility ( Im [ χ (3) ]) of 5.86 × 10 −11  esu, representing a 1.68-fold enhancement over ZnTBrPP. Similarly, ZnTPyPP-CMP showed a 1.41-fold increase in NLO performance. This enhancement is attributed to the synergistic effects of photo-induced electron/energy transfer (PET/ET), extended π-conjugation, and the CMP architecture that effectively inhibits porphyrin aggregation. Notably, ZnTFcPP-CMP exhibited a transition from saturable absorption (SA) at 5 μJ to reverse saturable absorption (RSA) at 50 μJ, a switching behavior driven by Pauli blocking and the transition from single-to two-photon absorption. Furthermore, solid-state optical plastic devices were fabricated by incorporating these CMPs into PMMA. At 50 μJ, the ZnTFcPP-CMP/PMMA and ZnTPyPP-CMP/PMMA composites exhibited Im [ χ (3) ] values 1.64 and 1.56 times higher than that of ZnTBrPP/PMMA, respectively. These results demonstrate that the construction of CMPs is a robust strategy for designing high-performance porphyrin-based materials for advanced NLO applications.