Metalation Sequence Modulates CO ₂ ‐To‐Cyclic Carbonate Conversion With Porphyrin–Polyurea Covalent Organic Polymer Catalysts

ABSTRACT A novel series of porphyrin–polyurea covalent organic polymers (COPs) was designed for CO 2 –epoxide cycloaddition to systematically investigate the influence of metalation sequence on structural ordering and catalytic behavior. Two cobalt–porphyrin‐based COPs, PUa‐CoDPP and PUa‐DPPCo, were synthesized through pre‐metalation and post‐metalation strategies employing amine‐isocyanate polycondensation and solution‐phase metal coordination, respectively. Comprehensive characterization revealed that the pre‐metalated system maintains high crystallinity, hierarchical porosity, and homogeneous dispersion of Co–N 4 sites via controlled monomer assembly, whereas the post‐metalated counterpart exhibits structural degradation and heterogeneous active sites due to coordination constraints within the preformed framework. In the solvent‐free cycloaddition of CO 2 and propylene oxide, PUa‐CoDPP achieves a near‐quantitative yield (> 99%) and exhibits superior recyclability, substantially outperforming PUa‐DPPCo. This performance disparity is mechanistically attributed to three sequence‐dependent factors: coordination completeness of active sites, framework‐regulated metal accessibility, and pore architecture‐mediated substrate diffusion. This study establishes the metalation sequence as a decisive design parameter for engineering high‐performance metalloporphyrin polymers that reconcile catalytic efficiency with operational durability.