Accessing high-order multiphoton excited fluorescence (H-MPEF) materials is challenging yet and needs complicated synthesis procedures. In this study, we successfully assembled plasmonic Au nanorods (Au NRs) with multiphoton responsive metal-organic frameworks (MOFs), resulting in a significant several-fold enhancement of H-MPEF. The extent of multiphoton enhancement was found to be strongly dependent on the degree of overlap between the multiphoton excitation wavelength of MOFs and the localized surface plasmon resonance absorbance of Au NRs, indicating the importance of plasmon-induced resonance energy transfer. Besides, plasmon-induced hot electron transfer played a vital role in enhanced multiphoton activity as well. Notably, the optimum H-MPEF enhancement occurs at the second near-infrared (NIR-II) region, which provides a promising platform for fluorescent bioimaging. Our findings provide a feasible and practical method to fabricate optimized H-MPEF materials for biological imaging using tissue-penetrating NIR-II light.

While metal nanoparticles (NPs) have shown great promising applications as heterogeneous catalysts, their agglomeration caused by thermodynamic instability is detrimental to the catalytic performance. To tackle this hurdle, we successfully prepared a functional and stable porphyrinic metal-organic framework (MOF), PCN-224-RT, as a host for encapsulating metal nanoparticles by direct stirring at room temperature. As a result, Pt@PCN-224-RT composites with well-dispersed Pt NPs can be constructed by introducing pre-synthesized Pt NPs into the precursor solution of PCN-224-RT. Of note, the rapid and simple stirring method in this work is more in line with the requirements of environmental friendly and industrialization compared with traditional solvothermal methods.