In this work, we have demonstrated CdS QD gels as a capable d-HAT photocatalyst to activate C-H bonds in various substrates, including cyclic ethers, amides, aldehydes, and benzylic compounds, to generate α-ethereal, α-amido, acyl, and benzylic radicals and enable versatile radical-based coupling reactions. The redox potential mismatch between the excited QD gel and C-H substrates, solvent, and base insensitivity suggests that C-H bond activation is unlikely to proceed via a sequential electron transfer and proton transfer pathway. The linear correlation between the log of rate constants and the C-H BDEs with a Brønsted slope α = 0.5 indicates that C-H bond activation should proceed via a d-HAT mechanism, in which photoexcited CdS QD gels directly attract a hydrogen atom from the C-H substrate. The H •doped CdS (CdS • -H) formed after H atom abstraction during the d-HAT process was also observed. The discovery of CdS as a new group of d-HAT catalysts will enrich the currently limited d-HAT catalysis toolbox and provide unique bondcleaving and forming capabilities for organic transformations.