Two‐Dimensional Conjugated Metal‐Organic Framework/Graphene π–π Stacked Heterostructures for Ultrafast Photonics

Abstract 2D conjugated metal‐organic frameworks (MOFs) with high in‐plane‐π‐conjugation are attracting significant attention in various fields owing to their outstanding electrical transport property, substantial specific surface areas, and tunable structures. However, their potential in ultrafast photonics has not been extensively explored. Herein, 2D conjugated Ni 3 (HITP) 2 metal‐organic framework (MOF) and graphene (GR) π–π stacked vertical heterostructures (NG‐VHS) are synthesized using an ultrasound‐assisted method. Based on theoretical simulations and characterization analyses, the results suggest that the fast interface charge transfer and the extension of the π‐conjugated electron cloud will significantly enhance the electrical conductivity and the nonlinear optical properties, which is attributed to the π–π stacking interactions between Ni 3 (HITP) 2 and GR. The charge transfer rate of NG‐VHS is given by 6.9 × 10 11 s −1 . Noticeably, NG‐VHS can serve as an excellent saturable absorber (SA) that can achieve fundamental mode‐locking with a pulse width of 451 fs, harmonic mode‐locking with repetition frequencies up to 1.205 GHz, and tunable dual‐wavelength mode‐locking. These results indicate the potential of NG‐VHS as a promising nonlinear optical material for ultrafast optical applications and a new platform for the design of advanced optoelectronic devices based on 2D conjugated MOFs.