Aqueous Synthesis of Covalent Organic Frameworks as Photocatalysts for Hydrogen Peroxide Production

Covalent organic frameworks(COFs)are crystalline porous polymers with designable structures and properties.Their crystallization typically relies on trialand-error experimentation involving harsh conditions,including organic solvents,presenting significant obstacles for rational design and large-scale production.Herein,we present a liquid crystal-directed synthesis methodology and its implementation for up to gram-scale production of highly crystalline COFs in water and air.It is compatible with monomers of different structures,shape,size,length of side chains,and electron-donating,electron-accepting,and heterocyclic substitutions near reactive sites.Seventeen types of donor-acceptor two-dimensional COFs including four types of new ones and a three-dimensional COF with a yield of up to 94%were demonstrated,showing great generality of the method.The as-synthesized donor-acceptor COFs are organic semiconductors and contain macropores besides intrinsic mesopores which make them attractive catalysts.The production of H_(2)O_(2)under visible light in water was studied and the structure-property relationships were revealed.The production rate reached 4347μmol h^(−1)gcat^(−1),which is about 467%better than that of the benchmark photocatalyst g-C_(3)N_(4).This study will inspire the mild synthesis and scale-up of a wide spectrum of COFs and organic semiconductors as efficient catalysts,promote their structure-property investigation,and boost their applications.

Synthesis of Thin Film of a Three-Dimensional Covalent Organic Framework as Anti-counterfeiting Label

Film plays a key role in the sustainable development of our society.Freestanding thin films of two-dimensional covalent organic frameworks(coFs)have been produced by interface,spin coating,microwave-assisted synthesis,and screen printing methods and are applied in nanofitration,molecular separation,photochemical sensing,anion transport,heat conduction,and proton conduction.On the other hand,the synthesis of their three-dimensional(3D)analogues and subsequent integration in devices remains challenging.Herein,self-supporting thin films of a three-dimensionai COF with tunable thickness was created by a stearic acid mediated synthesis methodology on water surface at room temperature in air.The film could be transferred onto arbitrary substrate,and when supported on indium tin oxide glass,it exhibited irreversible electrochromism.The optical feature made it act as a one-time anti-counterfeiting label in an electrochemical device.This work will inspire the synthesis of thin films of 3D COFs as well as other 3D materials,and boost their property and application exploration.

Surfactants Mediated Synthesis of Highly Crystalline Thin Films of Imine-Linked Covalent Organic Frameworks on Water Surface

Imine-linked covalent organic frameworks(COFs)have attracted extensive attention due to designable structures,tunable properties,and excellent thermal and chemical stability.They were typically obtained as insoluble and unprocessable powders,which seriously limits their full promise.Progress has been made in the synthesis of thin films of imine-linked COFs by interfacial synthesis.However,the synthesis of highly crystalline,self-supporting thin films of COFs remains challenging.Here,we employed a surfactants-mediated method to synthesize such films at an air-water interface,showed the films could be transferred onto arbitrary substrates on demand,and demonstrated the generality of the methodology with two different COFs.We found that the length of hydrophobic segments of surfactants played a key role in determination of the crystallinity and single crystalline domain size of the films.This work provides a feasible strategy to generate highly crystalline thin films of COFs.