Upconversion Lanthanide‐based Two‐dimensional Metal‐Organic Frameworks for Multi‐Mode Information Encryption

Luminescent 2D metal‐organic frameworks (MOFs) are a class of metal‐organic framework materials expanded in a two‐dimensional plane, which have a wide range of applications in fields of optoelectronic devices, sensors, and information storage due to their unique layered structure and excellent optical properties. Currently, research on luminescent 2D MOFs mainly focuses on down‐shifting luminescence, while the exploration of upconversion luminescence remains in its early stages. Herein, a novel two‐dimensional Yb‐PMA MOFs were synthesized, and red upconversion luminescence at 660 nm under 980 nm excitation was successfully achieved by introducing Ho3+ as the luminescence center and using Yb3+ as the sensitizer. In addition, multi‐mode emitting MOFs with both upconversion and down‐shifting luminescence were further constructed by co‐doping Tb3+ or Eu3+. Inspired by the layered structure of 2D materials, multilayer stacked 2D MOFs composites were prepared by ultrasonic exfoliation method and upconversion luminescence was realized for the first time by interfacial energy transfer between different components. This strategy not only expands the optical modulation of luminescent 2D MOFs, but also provides new ideas for the construction of multifunctional luminescent materials. The upconversion/down‐shifting luminescent lanthanide‐based 2D MOFs designed in this work show good potential for application in the field of information encryption.