Charge-mediated Cu^δ+ sites in dimension-controlled covalent organic frameworks enable base-free continuous...

The structural topology of covalent organic frameworks (COFs) critically governs their catalytic performance. However, the structure-property correlation regarding dimension-dependent charge polarization at catalytic sites remains poorly understood. Herein, we describe a dimensional engineering strategy to tailor the local microenvironment of Cu sites through constructing phenanthroline-based COFs with distinct architectures (2D vs 1D). Systematic characterization and theoretical analyses reveal that the molecular flexibility and mesoporous channels in 2D COFs promote non-radiative transitions and mass transport, while their layered architecture enables light-controlled thermal modulation of Cu^δ+ (1 ≤ δ ≤ 2) electronic states, synergistically enhancing substrate adsorption and activation. Remarkably, a Cu-2D-COF achieves near-quantitative yield (99.9%) in visible-light-driven carboxylative cyclization of propargylic amines with CO₂ under base-free conditions. We further engineered a continuous-flow photocatalytic system that demonstrates exceptional operational stability, delivering 2.143 g of pharmaceutical-grade 2-oxazolidinones with >95% purity. This work provides strategies for manipulating the local microenvironment through dimension-controlled frameworks in CO₂ conversion.