Metal–Organic Framework-Encapsulated Anthraquinone for Efficient Photocatalytic Hydrogen Atom Transfer

Anthraquinone (AQ) as an effective hydrogen atom transfer catalyst was limited in photocatalysis application due to the dimerization of reduced AQ. Sr-NDI@AQ, encapsulating AQ into the channel of Sr-NDI, paved a new way for solving the problem of dimerization of reduced AQ and improving the catalytic efficiency owing to the fast electron transfer from reduced AQ to the ligand through host-guest interaction. The structure of Sr-NDI@AQ was determined by single-crystal X-ray diffraction, and the value for distance and torsion angle between the ligand and AQ was calculated. The photochemical and electrochemical properties for Sr-NDI@AQ were characterized through a series of experiments. The coupling reaction between aldehyde and phenyl vinyl sulfone and photoacetalization reaction were carried out, displaying the improving catalytic efficiency of Sr-NDI@AQ compared to Sr-NDI and AQ. The reaction mechanisms were proposed through radical capture and electron paramagnetic resonance experiments.