Controllable Modulation of Third‐Order NLO Properties by Polymer‐Modified MOFs Core@Shell Nanoarchitecture

Abstract The delocalization and rearrangement of π electron clouds in space is the crucial source of regulating nonlinear optical (NLO) performance. Herein, a core‐shell metal organic framework (MOF)‐heterojunction is constructed to achieve the effect of tuning NLO properties by promoting charge transfer through multiple interactions between heterogeneous interfaces. [Cd(L)(4,4′‐bpy)(H₂O)]_n (Cd‐MOF) is selected to coat on polyaniline (PANI) surface to form PANI@Cd‐MOF. The constructed heterojunction displays an enhanced reverse saturation absorption (RSA) signal compared with Cd‐MOF, and it should be noted that the third‐order NLO refractive behavior changes from the self‐defocusing of Cd‐MOF to the self‐focusing of PANI@Cd‐MOF. It is proposed that high‐speed electronic communication bridges established via the rich hydrogen bond network (O… H‐N) and π–π interactions between heterogeneous interfaces can effectively modify the π electron cloud density that finally regulates the NLO properties. This work is believed to provide new avenues and insights for the design of third‐order NLO materials.