The guest CH_(3)CN molecule triggers solid-state photochromism in a Cu_(2)I_(2)-based MOF for advanced time-dependent encryption and inkless erasable printing

It remains a big challenge to develop solid-state stimuli-responsive materials for time-dependent information encryption and inkless erasable printing with long retention times.Herein,a 2D Cu_(2)I_(2)-based MOF with photoresponsive spiropyran(SP)groups orderly installed on its skeleton is developed.The structural isomerization from SP to colored merocyanine(MC)form can be triggered by removing the CH_(3)CN guests.Besides,the degree of structural isomerization and the retention time can be adjusted by controlling the amount of CH_(3)CN guests,exhibiting dynamic photochromic behavior with multicolor states and tunable retention time.Based on these advantages,time-dependent information encryption is successfully achieved.Furthermore,the long retention time(>72 h)of the MC form under daylight conditions in the CH_(3)CN-removed Cu_(2)I_(2)-based MOF and good repeatability make it promising in various applications,such as temporary calendars,price-cards,billboards,and reusable identity cards.This work provides a novel design strategy to fabricate multi-functional MOF-based smart materials for challenging applications of time-dependent information encryption and inkless erasable printing.