Fig.1 (A) Molecular structures of the TADF PSs with corresponding abbreviations. (B) Steady-state UV–vis absorption (solid lines), normalized emission (dashed lines) spectra. (C) TRPL decay traces of PSs. All spectra were recorded in Ar-saturated CH3CN with 450 nm excitation. Trace colors: 4DPAIPN (red), 4Br-DPAIPN (blue), 4PY-DPAIPN (yellow).#

Fig.2 (A) Contour plots depicting the temperature-dependent emission spectral evolution of the PSs in 2-MeTHF. (B) Steady-state photoluminescence, (C) time-resolved phosphorescence, and (D) time-resolved fluorescence spectra recorded at 77 K. Trace colors: 4DPAIPN (red); 4Br-DPAIPN (blue); 4PY-DPAIPN (yellow).#

Fig.3 (A) CVs of the organic PSs (0.5 mM) in Ar-saturated CH3CN with 0.1 M nBu4NPF6 as the supporting electrolyte at a scan rate of 100 mV/s. (B) Energy level diagram summarizing the measured half-wave reduction potentials, oxidation peak potentials, and the corresponding estimated energies of the singlet and triplet excited states. Trace colors: 4DPAIPN (red), 4Br-DPAIPN (blue), and 4PY-DPAIPN (yellow).#

在光催化二氧化碳还原测试中，研究人员将光敏剂与廉价的四羧基酞菁钴（CoTCPc）催化剂及牺牲剂BIH配对，在450 nm可见光照射下进行反应（如图4）。在最优条件下，4Br-DPAIPN体系展现出惊人的光催化活性与选择性，初始反应速率达到3.3 $\mu\text{mol}\cdot\text{min}^{-1}$，CO选择性超过98%，在15分钟内的CO生成量子产率（$\text{QY}_{\text{CO}}$）高达49.8% ± 5.3%（如图4）。该性能不仅显著高于母体4DPAIPN体系（42.3%）与4PY-DPAIPN体系（8.6%），更达到了钌基准配合物体系的10倍以上（如图4）。碳13同位素标记实验（$^{13}\text{CO}_2$）确证生成的产物全部源自气相二氧化碳底物。

Fig.4 Molecular structures of (A) the catalyst CoTCPc and (B) the referenced precious-metal-based PSs. (C) Time profiles of photocatalytic CO (star) and H2 (circle) formation with 0.5 mM PS and 0.05 mM CoTCPc under 450 nm irradiation. (D) CO and H2 yields obtained with different BIH concentrations for systems containing 4DPAIPN or 4Br-DPAIPN after 15 min or 2 h of irradiation. (E) QYCO for CO production at 15 min under 450 nm irradiation. Standard condition: PS (0.5 mM), CoTCPc (50 µM), phenol (4.0 v%), BIH (50 mM) in 4 mL CH3CN/TEA (v = 5<1>) with 450-nm LED irradiation under 1 atm CO2. The error bars represent the standard deviations of three independent measurements.#

通过瞬态发光猝灭实验与激发态动力学定量分析，研究团队阐明了体系性能差异的深层机理。在光催化工作浓度下，还原猝灭占绝对主导；对于4PY-DPAIPN，其激发态氧化能力的提升显著加速了单重态猝灭速率（$6.0 \times 10^8 \text{ s}^{-1}$），导致单重态在发生系间窜越前大量被无效消耗；而4Br-DPAIPN凭借重原子效应赋予的超快系间窜越速率（$7.1 \times 10^8 \text{ s}^{-1}$），在竞争中以4.5倍的显著优势压倒了单重态猝灭途径。这种内源性的动力学优势最大限度地将光激发能量引导至长寿命三重态，进而高效生成具有高逃逸产率的催化活性自由基阴离子，从微观机制上实现了反应路径的精准转向。

Scheme 1 Reductive quenching processes of the singlet and triplet excited states of PS by BIH.#

Scheme 2 Proposed energy and electron transfer processes for the PS/CoTCPc/BIH system.#