Atomically precise copper nanoclusters have emerged as a promising class of catalysts. However, the exploration of copper nanocluster catalysts has been slow, likely because of their complicated synthesis, limited stability, and low activity under mild conditions. Herein, we present highly stable copper nanoclusters [Cu₈(S₂CN(CH₃)₂)₆(PPh₃)₄]²⁺ (where S₂CN(CH₃)₂ is dimethyldithiocarbamate and PPh₃ is triphenylphosphine) with facile synthesis and high photocatalytic performance. The nanoclusters were obtained on a gram-scale through a one-pot reduction of Cu(S₂CN(CH₃)₂)₂ with (PPh₃)₂CuBH₄ in the presence of 3,5-bis(trifluoromethyl)pyrazole. Comprehensive experimental and theoretical characterization of the nanoclusters was performed to elucidate their atomic and electronic structure and explain their high stability under light irradiation. Importantly, the nanoclusters exhibit photocatalytic activity in the difluoroalkylarylation of alkenes at room temperature, yielding a wide range of complex difluoromethyl compounds under mild conditions. This study not only presents an efficient strategy for the synthesis of copper nanoclusters with atomically precise and highly robust structures but also highlights the potential of atomically precise copper nanocluster catalysts in the rapid construction of molecular complexity with substantial material economy.