Modification of covalent organic frameworks surface using thermal sensitivity polymers

Covalent organic frameworks (COFs) represent an exciting new type of porous organic materials, which are ingeniously constructed with organic building units via strong covalent bonds. Boronic acids are one of versatile building blocks for the construction of complex molecular architectures.1,2 Most notably, the formation of boronate esters has been used extensively in carbohydrate chemistry, where boronic acids have found applications as protecting groups or as receptors and sensors. Using reversible condensation reactions, it is possible to obtain macrocycles, cages, and dendritic structures. The creation of cage structures requires building blocks, which are able to connect more than two reaction partners. Molecular modeling showed that the cage has a cavity with approximate dimensions of 27A˚. Guest molecules such as monomers, fluorescein molecules, and drugs are able to encapsulate by the cage of COF.3,4Here we synthesize 2D boronate ester-linked COF under conditions in which the monomers are fully soluble. Then, thermo‐responsive poly(N‐isopropylacrylamide) (PNIPAM) was growled inside the cavity of synthesized COF through radical polymerization. The as‐prepared modified COFs integrated the individual advantages of two components, such as the thermal sensitivity of the PNIPAm terminal as well as pH sensitivity of the COF substrate. This smart COF has shown remarkable potential for intelligent strain sensors, textiles, actuators and on/off switches.

Keywords:

Covalent organic frameworks (COFs) , Boronic acid , Poly(N-isopropylacrylamide)