Tunable Anti‐Thermal Quenching Luminescence of Eu3+‐Doped Metal‐Organic Framework and Temperature‐Dependent Photonic Coding

Applications of luminescence at high temperature such as high‐power lighting, lasing, thermophotovoltaics, and photonic coding, are severely prevented due to the notorious thermal quenching (TQ). Although anti‐TQ luminescence (anti‐TQL) is reported using highly oxygen‐coordinated solid‐state oxide as host in virtue of the rigid skeleton that resists lattice vibration at elevated temperatures, it is meaningful to extend anti‐TQL to other hosts. Herein, taking advantage of the ligand‐metal antenna effect and the negative thermal expansion feature of Eu3+ doped MIL‐68‐In (MIL‐68‐In/xEu), adjustable anti‐TQL is realized for the first time, that is, anti‐TQ, zero‐TQ, and TQ at x = 5%, 10%, and 50%, respectively. Therefore, except for added novel mechanisms, this work has also expanded the hosts available for high‐temperature luminescence and enabled advanced photonic coding in terms of facial synthesis, rich information, and visual changes of emission intensity instead of device‐dependent analogous. Upon heating, symmetry reduction around Eu3+ site caused by anisotropic contraction of MIL‐68‐In framework and Boltzmann population between 7F0 and 7F1 levels of Eu3+, together lead to thermally enhanced luminescence. Further modulation of Eu3+ concentration in MIL‐68‐In/Eu allows modulation of thermal‐responsive emissions toward advanced information encryption.