Coordination-directed synthesis of two-dimensional metal-organic covalent organic frameworks

Metal-organic covalent organic frameworks (MOCOFs) combine the advantages of covalent and metal-organic frameworks, but research remains sparse due to characterization difficulties, leaving unclear whether their formation is covalent- or coordination-directed. To date, only a few three-dimensional MOCOFs have been reported, while two-dimensional (2D) MOCOFs remain unexplored. Here, we strategically synthesize two single-crystal 2D MOCOFs with high porosity, denoted as PUMC-1 and PUMC-2. Leveraging three-dimensional electron diffraction, we are able to elucidate their formation process in detail. First, one-dimensional coordination polymers (1D CPs) are constructed from two sub-building units: tetrakis(4-aminophenyl) porphyrin and cobalt(II) trans-A₂B₂ porphyrin. Second, 1D CPs with covalent extension sites are used to construct two distinct 2D MOCOF conformations via covalent self-assembly under different conditions. Notably, the same 2D MOCOFs can also be directly obtained via one-pot synthesis with the same monomers, providing experimental evidence for a coordination-directed covalent assembly mechanism. This work not only expands the dimensionality of MOCOFs but also opens new avenues in reticular chemistry. Metal-organic covalent organic frameworks (MOCOFs) combine the advantages of covalent and metal-organic frameworks, but two-dimensional (2D) MOCOFs remain unexplored. Here, the authors synthesize two 2D MOCOFs with high porosity and elucidate their formation process in detail.