Donor-Acceptor Metal-Organic Frameworks Featuring Tunable Triplet States for Multistimulus Responsive Room-Temperature Charge Transfer Phosphorescence

Room-temperature phosphorescence (RTP) has drawn considerable attention due to its fascinating applications. Herein, we report the achievement of multistimulus responsive RTP by utilizing the customizable donor-acceptor (D-A) metal-organic framework (MOF) platform for charge -transfer (CT)-based triplet state tuning. A succession of electron-rich donors was introduced into the triazinebased electron-deficient framework (NKU-Mg-2) to give D-A MOFs (A1-A3) featuring CT-based emission. Notably, donors are designed and guided by heavy atom effect (-Br) to enhance the spin-orbit coupling, thereby achieving a fine-tuning excited state, resulting in the manipulation of phosphorescence from low temperature (A1) to room temperature (A2). Moreover, enhanced RTP intensity is further achieved by facilely altering the halogen functionalization (A3). The modulated A3 simultaneously achieves multiple stimulus responses to X-ray, temperature, and oxygen, rendering it a promising candidate for novel optical sensors. This work not only achieves flexible control over the excited state but also presents a novel approach for developing multistimulus responsive intelligent optical materials.