1 Department of Chemistry, College of Sciences, Shanghai University, Shanghai, 200444, China.
2 Department of Chemistry and Biochemistry and Centre for NanoScience Research, Concordia University, Montreal, QC H4B 1R6, Canada.

Luminescent 2D metal-organic frameworks (MOFs) are a class of metal-organic framework materials expanded in a 2D 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 2D 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, multimode emitting MOFs with both upconversion and down-shifting luminescence were further constructed by codoping 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.