In Situ Loading of\nZnS on the PPF‑3 Surface\nfor Enhancing Nonlinear Optical Performance

In recent years, with the rapid development of ultrastrong\nand\nultrafast lasers, it has become essential to develop new materials\nwith excellent nonlinear optical (NLO) properties. Porphyrin-based\nmetal–organic frameworks (MOFs) have great potential for application\nin the field of NLO due to their large conjugated structure and good\nstability. As a typical porphyrin-based MOF, porphyrin paddle-wheel\nframework-3 (PPF-3) has been prepared and applied in the fields of\ncatalysis and sensing, yet the investigation of PPF-3 in NLO remains\nunexplored. In this study, the ZnS/PPF-3 composite was successfully\nprepared using a solvent thermal method to in situ load ZnS on the\nsurface of PPF-3. Utilizing the Z-scan technique, the NLO properties\nof ZnS, PPF-3, and ZnS/PPF-3 composite were investigated under different\ninput energy intensities. ZnS/PPF-3 composite material exhibits significantly\nenhanced NLO properties, with the third-order nonlinear absorption\ncoefficient (β<sub>eff</sub>) of up to 7.00 × 10<sup>–10</sup> m/W and a limiting threshold as low as 1.52 J/cm<sup>2</sup>, indicating\nits promising application potential value in the field of optical\nlimiting. To enhance the practical utility, the ZnS/PPF-3/PVA film\nwas prepared via the drop-casting method, achieving a maximum β<sub>eff</sub> of 5.00 × 10<sup>–8</sup> m/W. The smaller\noptical bandgap of ZnS/PPF-3 and electron transfer from PPF-3 to ZnS\nare the key factors that enable the ZnS/PPF-3 composite to a superior\nNLO performance.