Single Crystal of a One-dimensional Covalent Organic Framework

Although polymers have been studied for well over a century, there are few examples of covalently linked polymer crystals synthesized directly from solution. One-dimensional (1D) covalent polymers that are packed into a framework structure can be viewed as a 1D covalent organic framework (COF), but making single crystal of this has been elusive. Herein, by combining labile metal coordination and dynamic covalent chemistry, we discovered a strategy to synthesize single-crystal metallo-COF under solvothermal conditions. The single-crystal structure was rigorously solved using single-crystal electron diffraction (SCED) technique. The non-centrosymmetric metallo-COF allows second harmonic generation (SHG). Due to the presence of syntactic pendant amine groups along the polymer chains, the metallopolymer crystal can be further cross-linked into a crystalline woven network.