Carbon-based frameworks for chemical control
COFs have networks of pores that can be designed to selectively bind and retain specific molecules. Credit: Ming-Xue Wu and Ying-Wei Yang
Covalent organic frameworks promise exciting new applications for industry, electronics and medicine
Chemists worldwide are busy linking carbon-based ‘organic’ molecules together in a huge variety of ways, much like children playing with snap-together toys. Such covalent organic frameworks (COFs) show potential for many applications, including gas storage and separation, catalysis,
light-controlled electronics, environmental sensing, and drug delivery.
Ming-Xue Wu and Ying-Wei Yang of Jilin University in China have published a concise review of research toward developing applications for COFs, in Chinese Chemical Letters. “We hope that our review will encourage even more research groups to get involved,” says Yang.
The key components of COFs are a wide variety of carbon-based building blocks that are joined up by
‘linker’ groups of varying lengths and structures, held together by ‘covalent’ bonds. These are the strong chemical bonds that bind atoms within molecules. But in COFs, they create giant and stable frameworks with extended networks of internal pores and channels.
The porosity of COFs is a key feature. They form solid crystalline materials that could store gases for use as fuels, or could selectively retain specific gases to capture pollutants or separate gas mixtures. If methane and hydrogen are to become viable alternative fuels, for example, the prodigious storage capacity of solids such as COFs may prove useful.
COFs also look promising for optoelectronics as in some cases their semi-conductive properties are controlled by interactions with light. Additionally, the presence of specific chemicals can be signalled by altered optical properties such as fluorescence, perhaps forming the basis of environmental sensors.
Drug delivery is another possibility as the pores of COFs are ‘tunable’ spaces that can be used to
carry drug molecules to a destination, such as a tumor. The targeted release could be triggered by an existing change in the chemical environment, or perhaps by an external stimulus, such as light or heat. COFs are also being explored as new catalysts for industry.
The applications for COFs are largely experimental for now, but Yang and his colleagues see “a bright future.” They report that “remarkable progress has been made,” since COFs were first created ten years ago.
These materials are a more recent innovation than the better known metal-organic frameworks (MOFs) for which a similar range of applications are being developed. With COFs and MOFs to play with, chemists seem sure to deliver many new versatile porous materials to become key components
of industrial, technological, and medicalinnovations of the near Future.
Wu, M-X and Yang,Y-W.: Applications of covalent organic Frameworks (COFs):From gas storage and separation to drug delivery." Chinese ChemicalLetters (2017)