Photochromic Metal–Organic Framework for High-Resolution Inkless and Erasable Printing

Inkless
and erasable printing as a new technology has received
intense attention in reducing paper waste and environmental hazards
caused by the use of large amounts of ink. However, achieving high-resolution
printing by inkless and erasable printing for practical applications
remains a huge challenge. Herein, a new metal–organic framework
(MOF) has been synthesized, which exhibits a reversible photochromic
behavior. None of the unpaired electrons of metal ions and a unique
three-dimensional network hinder electron transfer between the ligands
and metal nodes, as well as between the ligands themselves, which
are conducive to prolonging the photo-generated color lifetime and
suitable for inkless and erasable printing. By virtue of the proper
photo-generated color lifetime, strong contrast color before and after
light irradiation, and reversible color transformation, a high-resolution
printing content for inkless and erasable printing can be achieved
by light irradiation. Notably, the paper coated with this MOF can
be used for printing not only simple patterns such as pictures but
also even texts for practical applications, surpassing other photochromic
MOF materials for inkless and erasable printing, and almost comparable
to ink and laser printing in terms of practicality and resolution.
In addition, the MOF-coated paper can be reused for multiple cycles
without significant deterioration.