Steering from C₁ to C₂ Products from the Photocatalytic CO₂ Conversion over Correlated Single-Atom Pairs

The urgent need to mitigate accelerating CO₂ emissions has driven intense interest in photocatalytic CO₂ reduction (CO₂RR), a process that mimics natural photosynthesis to generate carbon-neutral, value-added chemicals. While efficiency has improved, the selective production of high-value C₂₊ products rather than C₁ compounds remains a critical challenge to economic viability. Single-atom catalysts offer promise for steering selectivity, yet how atomic-scale spatial distribution dictates reaction pathways remains poorly understood. Here, we demonstrate a programmed spatial distribution approach to induce synergistic cooperativity between neighboring Cu motifs within a UiO-67 matrix. By precisely modulating site distribution, we reveal a spatial threshold at which the framework transitions from isolated sites favoring C₁ products to correlated single-atom pairs (CSAPs) that facilitate C-C bond formation. Temperature-resolved electron paramagnetic resonance spectroscopy provides compelling evidence for the distribution-dependent proximity, capturing a unique magnetic feature that emerges as torsional linker motions are suppressed. This structural configuration utilizes the inherent rotational flexibility of the linkers to dynamically optimize interatomic distances, effectively stabilizing [OC-CO]* dimer intermediates and steering the reaction toward C₂ products.