Acid-base Induced Structural Deformable 2D Covalent Organic Framework

Despite the rapid progress of synthetic two-dimensional covalent organic networked?2D-CON?nanomaterials,it remains a great challenge to prepare such materials with both precise long-range lateral orders and structural deformability.Currently reported 2D-CON materials are mainly synthesized by reversible dynamic covalent chemical reaction between rigid symmetrical monomers.This strategy makes the prepared 2D-CON materials often suffer from poor structural deformability,which limits their application scopes.In this dissertation,a new strategy based on noncovalent pre-organized macrocyclic monomers is developed for the first time to construct structurally deformable 2D covalent framework?2D-COF?with unique noncovalently connected skeleton.First of all,an unconventional macrocyclic diamine monomer containing preorganized quadruple hydrogen-bonded ureidopyrimidinone?UPy?modules was designed and synthesized,through the solvothermal condensation of which with1,3,5-trimethyl-phloroglucinol we successfully fabricated 2D UPy-COF incorporated with quadruple hydrogen-bonded UPy patterns.A series of characterization experiments including FT-IR spectra,solid-state ¹H and ¹³C NMR spectra,PXRD profiles and calculation simulation,as well as SEM and TEM images have provided strong arguments for the distinctive 2D layered structure of UPy-COF.Furthermore,upon protonating the as-obtained UPy-COF with trifluoroacetic acid?TFA?,the quadruple hydrogen bonds in the dimerized UPys is able to be disassociated,resulting in the structural deformation of UPy-COF.The 2D structure of UPy-COF can be reformed by treating the acidified sample with Et₃N via the reconstruction of the quadruple hydrogen-bonded UPy connections.This dissertation not only successfully prepares a new type of 2D COF material with distinctive structure,but also develops a general strategy for designing and constructing diverse synthetic nanomaterials which concurrently features structural regularity and deformability.