Most of the current fluorescence sensing materials belong to the turn-off type, which make it hard to detect toxic substances such as benzene, toluene, and xylene (BTX) due to the lack of active chemical sites, thereby limiting their development and practical use. Herein, we show a guest–host mechanism stemming from the confined emitter’s self-trapped exciton (STE) states or electron–phonon coupling to achieve turn-on fluorescence. We designed a luminescent guest@metal–organic framework (LG@MOF) composite material, termed perylene@MIL-68(In), and established its E-type excimeric emission properties in the solid state. Upon exposure to BTX, especially xylene, we show that the E-excimer readily converts into the Y-excimer due to nanoconfinement of the MOF structure. Such a transformation elevates the fluorescence intensity, thus realizing a turn-on type fluorescent sensor for detecting BTX solvents. Our results further demonstrate that controlling the STE states of perylene at room temperature (vs the previous report of <50 K) is possible via nanoscale confinement, paving the way to enabling turn-on type luminescent sensors for engineering practical applications.

中文翻译：

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通过室温下自陷激子态的转变开启荧光化学传感

目前的荧光传感材料大多属于关断型，由于缺乏活性化学位点，难以检测苯、甲苯、二甲苯（BTX）等有毒物质，从而限制了其发展和实际应用. 在此，我们展示了一种客体-主体机制，该机制源于受限发射器的自陷激子 (STE) 态或电子-声子耦合以实现开启荧光。我们设计了一种发光的客体@金属-有机骨架 (LG@MOF) 复合材料，称为苝@MIL-68(In)，并确定了其在固态下的 E 型准分子发射特性。暴露于 BTX，尤其是二甲苯后，我们表明，由于 MOF 结构的纳米限制，E-准分子很容易转化为 Y-准分子。这种转变提高了荧光强度，从而实现了一种检测BTX溶剂的开启型荧光传感器。我们的结果进一步表明，在室温下控制苝的 STE 状态（与之前报告的 <50 K 相比）是可能的通过纳米级限制，为工程实际应用启用开启型发光传感器铺平了道路。