Recent intriguing concepts have proposed that utilizing metal-organic frameworks (MOFs) as host matrixes can improve the crystallization of 9,10-diphenylanthracene (9,10-DPA) molecules in the solid film while also maintaining its high fluorescence quantum yield. Understanding the fundamental excited state dynamics is essential to the potential applications of these emerging materials, especially considering that photocarrier dynamics are expected to behave differently in the MOF structure due to the restricted degrees of freedom and long-range electronic couplings. Here, we have systematically investigated the carrier dynamics in highly crystalline and ordered DPA-MOF thin films employing transient absorption spectroscopy. Under photoexcitation, the constrained DPA molecules within the framework exhibit an ultrafast structural torsion in several hundred femtoseconds, which alters the energy positions of ${\mathrm{S}}_1$ states and blocks the ${\mathrm{S}}_0\to {\mathrm{S}}_1$ transition, enabling a strong localized excitation and the excimer formation. Sequentially, the localized photocarriers start to redistribute via the intramolecular singlet-to-triplet energy transfer and the interlayer singlet charge transfer. Furthermore, we have demonstrated that the photoinduced torsion and corresponding carrier dynamics can be effectively controlled by the excitation fluence.

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• Carrier dynamics
• Photoinduced effect
• Metal-organic framework
• Ultrafast femtosecond pump probe