Self-templated chemically stable hollow spherical covalent organic framework.

Sharath Kandambeth,Rahul Banerjee,V Venkatesh,Sandeep Verma,Sushma Kumari,Digambar B Shinde,Arjun Halder

doi:10.1038/ncomms7786

Abstract

Covalent organic frameworks are a family of crystalline porous materials with promising applications. Although active research on the design and synthesis of covalent organic frameworks has been ongoing for almost a decade, the mechanisms of formation of covalent organic frameworks crystallites remain poorly understood. Here we report the synthesis of a hollow spherical covalent organic framework with mesoporous walls in a single-step template-free method. A detailed time-dependent study of hollow sphere formation reveals that an inside-out Ostwald ripening process is responsible for the hollow sphere formation. The synthesized covalent organic framework hollow spheres are highly porous (surface area ∼1,500 m(2 )g(-1)), crystalline and chemically stable, due to the presence of strong intramolecular hydrogen bonding. These mesoporous hollow sphere covalent organic frameworks are used for a trypsin immobilization study, which shows an uptake of 15.5 μmol g(-1) of trypsin.

Highlights

Covalent organic frameworks are a family of crystalline porous materials with promising applications
Immobilization of enzyme into the mesoporous material is potentially useful for applications such as biosensors and biocatalysts because it can increase the recyclability of the costly enzyme and improves the stability of enzymes under extreme conditions[45,46,47,48]
Scanning electron microscopy (SEM) imaging of the COFDhaTab sample before and after treatment shows that the hollow sphere morphology of the Covalent organic frameworks (COFs)-DhaTab was lost after the base treatment and the morphology transforms into aggregated platelet-like structure (Supplementary Fig. 33). These results indicate that the hollow sphere morphology of COF-DhaTab gets disintegrated into small particles in the presence of NaOH, which may be the reason for the loss of crystallinity of DhaTab during NaOH treatment

Summary

Introduction

Covalent organic frameworks are a family of crystalline porous materials with promising applications. The synthesized covalent organic framework hollow spheres are highly porous (surface area B1,500 m2 g À 1), crystalline and chemically stable, due to the presence of strong intramolecular hydrogen bonding. Covalent organic frameworks (COFs) represent a new family of crystalline porous materials, with a well-defined and predictable network of molecular building blocks[1] These materials showcase promising applications in the field of gas storage[2,3,4,5], opto-electronics[6], catalysis[7,8,9] and sensing[10] because of their crystalline and periodic structure with high surface area and thermal stability. Immobilization of enzyme into the mesoporous material is potentially useful for applications such as biosensors and biocatalysts because it can increase the recyclability of the costly enzyme and improves the stability of enzymes under extreme conditions[45,46,47,48]

Methods

Results

Conclusion