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

Abstract

Main observation and conclusion 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.

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

“…The evaporation of chloroform promotes the diffusion of SA and facilitates its assembly to form monolayers at the air‐water interface with the hydrophobic alkyl chain towards the air and carboxyl group face the water. [ 27‐29 ] 400 μL of tetrakis(4‐aminophenyl)methane (TAM) protonated with 0.12 mol/L p ‐toluenesulfonic acid was then added to the solution. Carboxyl group of stearic acid will act as a template to guide the assembly of TAM thorough electrostatic interactions and the formation of hydrogen bonds, and further provides a 2D confinement for the polymerization of TAM.…”

Extremely Stable Sulfuric Acid Covalent Organic Framework for Highly Effective Ammonia Capture†

“…Recently, covalent organic frameworks (COFs) [ 15 ] have been emerging as a kind of crystalline materials and shown potential application in the fields of gas adsorption and separation, [ 16 ] catalysis, [ 17 ] sensing, [ 18 ] and proton conduction, [ 19 ] due to the large surface areas, tunable pore sizes, and ultrahigh chemical/thermal stabilities. [ 20 ] However, up to date, only limited examples reported the potential application in NH 3 capture even if they indeed showed outstanding adsorption performances. For instance, in 2010, Yaghi's group reported the first case of boronate ester COF as NH 3 adsorbent.…”

Microenvironment Modulation of Imine‐Based Covalent Organic Frameworks for CO2 Photoreduction

“…Covalent organic frameworks (COFs) are causing ripples among researchers striving to develop promising metal‐free photocatalysts. [ 19‐21 ] The particular advantages of COFs in photocatalysis are as follows: (i) the high crystallinity and ordered structure facilitate the investigation of the catalytic mechanism; [ 22‐24 ] (ii) the designability of their structure allows for targeted anchor of active catalytic units; [ 25 ] (iii) the large specific surface area endows them with abundant accessible catalytic sites; [ 26 ] (iv) the stable covalent bonds provide a guaranteed platform for catalytic reactions; [ 27‐28 ] (v) the π‐covalent structure extending in‐plane and in the stacking direction allows for efficient charge migration. [ 29 ] Currently, metal modification on the COF backbone has been the widely adopted strategy in photochemical CO 2 reduction, [ 30‐31 ] while the development of metal‐free COFs as catalysts and the investigation of the effect of the microenvironment of COFs on activity is still in its infancy.…”