This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers at the Center for Research in Biological Chemistry and Molecular Materials (CiQUS) at the Universidade de Santiago de Compostela (USC) have developed a new strategy for producing covalent organic frameworks (COFs) with semiconducting properties without relying on chemical doping. The approach could open new avenues for developing materials for applications in electronics and energy storage.
The work has been published in Angewandte Chemie International Edition under the title "Semiconducting Covalent Organic Frameworks Based on Spin-Delocalized Trioxotriangulene Neutral Radicals." COFs (Covalent Organic Frameworks) are materials made up of organic molecules connected by covalent bonds, forming ordered, crystalline structures with nanoscale pores. This combination of properties makes them attractive for applications ranging from electronics and sensing to energy storage. However, achieving efficient electrical conductivity in these materials remains challenging: In most cases, external substances known as dopants are required to provide the charge carriers needed for electrical conduction.
This process can alter the material's structure, reducing its crystallinity, porosity and stability. The CiQUS team has proposed an alternative approach: incorporating radical molecules directly into the COF structure so they can provide charge carriers without the need for post-synthetic doping. To achieve this, the researchers used neutral trioxotriangulene (TOT) organic radicals as building blocks.
These molecules are characterized by highly delocalized spin and remarkable stability. The strategy yielded a crystalline COF with semiconducting behavior and room-temperature electrical conductivity among the highest reported to date for neutral, non-doped COFs. At the same time, the material retains a high degree of porosity, with a specific surface area of more than 1,200 m² per gram.
A key feature of the approach is that the TOT radicals are not simply added to the material as an additional component: they form part of its molecular structure. Their unpaired electrons can generate charge carriers without the need for counterions or other external chemical species. The ordered arrangement of these units within the framework also facilitates charge transport through the material.
The result is particularly relevant because it brings together properties that are not always easy to maintain simultaneously: electrical conductivity, crystallinity and porosity. The study also shows that the framework can be modified by selecting different components and linkages, providing scope to tune the electronic properties of these materials. This versatility could prove useful in the future for developing materials for electronics, spintronics, sensors, electrochemical devices and energy storage.
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