Ln-MOFs with in-situ exsolved perovskite as ratiometric fluorescent for H2O and Cu2+: Spacial charge transfer and detection mechanism

Abstract

Herein, a ratiometric fluorescent sensor based on CPB⊆Pb/Eu-MOF heterojunction has been designed for rapid, sensitive and visual detection of H2O and Cu2+ in extraction solution. The energy transfer from Pb2+ to Eu3+ in Pb/Eu-MOF has enhanced the luminescent emission of Eu3+, and the CPB⊆Pb/Eu-MOF n-n heterojunction with S-scheme charge transfer can stabilize CPB to activate the detecting for H2O and Cu2+. In-situ XPS and XRD have confirmed the phase transformation from cubic CPB to CsPb2Br5 majorly contributes to color switch when being introduced by H2O. Moreover, the dynamic quenching and electron transfer are verified by the adsorption energy Br-Cu bonding according to DFT calculation and the shortened fluorescence lifetime. Typically, 0.2CPB⊆Pb/Eu-MOF composite exhibits a highly sensitive and selective ratiometric fluorescent sensing. The proper linear ranges from 10.80 % to 23.10 % and a low detection limit of 0.26 % for H2O, while 20–180 μM, R2 = 0.996, and 8.09 μM for Cu2+. More importantly, the paper-based sheet sensor has been manufactured practically in the real floral teas and different solvents for the visual detection of H2O and Cu2+ by naked eyes.