Kinetically Resolved C-N Coupling on Molecularly Engineered Co-Phthalocyanine Covalent Organic Frameworks for...

Electrochemical urea synthesis via NO3- and CO2 coreduction offers a sustainable route to valorize waste streams, but incomplete mechanistic understanding of C-N coupling hinders rational catalyst design. Using density functional theory, we investigate the C-N coupling network on three Co-phthalocyanine covalent organic frameworks (F-COF, BF-COF, B-COF). We establish a comprehensive mechanistic picture revealing two key selectivity nodes. First, CO2 preferentially couples with *NHO or *NHOH. F-COF exhibits a uniquely low barrier (0.12 eV) for *NHO-CO2 coupling, which projected density of states, Bader charge, and charge-density-difference analyses trace to a Co 3d manifold displaced toward the Fermi level and to the least polarized Co-N4 unit of the series. Bader charge analysis reveals that progressive charge accumulation on N intermediates (∼2 e) serves as a predictive, quantitative descriptor for optimal C-N coupling windows. Second, *CONH couples with *NH (0.36 eV barrier on F-COF) to yield *NHCONH, constituting the primary kinetic bottleneck. Free-energy profiling confirms that F-COF displays the optimal combination of a low rate-determining step (0.49 eV) and a continuously exergonic postcoupling cascade. These findings identify the combined macrocycle-linker electronic environment as the operative design lever and provide transferable descriptors for rational urea electrocatalyst development.