Polymorphism of 2D Imine Covalent Organic Frameworks

Abstract We designed and synthesized A 2 B 2 type tetraphenyl benzene monomers (p‐, m‐, and o‐TetPB) which have the para‐, meta, and ortho‐substituted isomeric structures, for the direct construction of isomeric frameworks. Interestingly, both kagome ( kgm ) and monoclinic square ( sql ) framework isomers are produced from either p‐TetPB (C 2h symmetry) or m‐TetPB (C 2v symmetry) by changing reaction solvents, while their isomeric structures are characterized by X‐ray diffraction, computational simulation, microscopy, and sorption isotherm measurements. Only sql frameworks was formed for o‐TetPB (C 2v symmetry), irrespective of reaction solvents. These results disclose a unique feature in the framework structural formation, that is, the geometry of monomers directs and dominates the lattice growth process while the solvent plays a role in the perturbation of chain growth pattern. The isomeric frameworks exhibit highly selective adsorption of vitamin B 12 owing to pore shape and size differences.