Excellence in Research Mechanochemistry as an Enabling Tool for the Synthesis, Modification, and Application of Covalent Organic Frameworks

PART 1: NON-TECHNICAL SUMMARY

As society faces critical challenges related to resource management, there is an urgent need to develop new synthetic approaches in material chemistry. Mechanochemistry, the science of using milling, shearing, and compressing to drive chemical reactions, has been recognized internationally as an important synthesis technique. Through this Excellence in Research (EiR) project researchers at Clark Atlanta University leverage mechanochemistry for the synthesis and transformation of covalent organic frameworks (COFs).

COFs are 2D or 3D crystalline porous polymers with precise integration of monomer units into extended periodic networks, representing one of the most emerging porous solids owing to their eminent structural features and widespread applications, for example in gas storage, catalysis, environmental remediation, cancer therapy, and battery technology. However, traditional synthesis methods of COFs require long reaction times (3-9 days), harsh conditions (high temperatures and vacuum), and the use of toxic solvents, limiting their widespread application.

The project advances insights into mechanochemical COF synthesis and enables the capability in the United States. The research plan includes the mechanosynthesis of COFs through multicomponent reactions, the development of COF-based composites, the application of COFs for radionuclide sequestration, and the elucidation of mechanochemical COF formation mechanisms.

Additionally, the educational plan integrates the research into a new graduate course, undergraduate research initiatives, and an outreach program related to mechanochemistry. By engaging postdoctoral researchers, graduate and undergraduate students, and K-12 students, this project provides exposure to frontier research which considerably expands the research capability at Clark Atlanta University.

PART 2: TECHNICAL SUMMARY

With this Excellence in Research (EiR) project researchers at Clark Atlanta University establish a solid-state mechanochemical synthesis methodology for the preparation of covalent organic frameworks (COFs) through mechanistic investigations and carry out proof-of-principle experiments aimed at radionuclide sequestration. Currently, full exploitation of the potential uses for COFs is hampered by synthetic hurdles associated with prevalent solvothermal synthesis, including long reaction times (3-9 days), high temperatures, hazardous organic solvents, anaerobic conditions, and limited scalability.

Therefore, the principal investigator and his team focus on mechanochemical approaches to synthesize, modify, and utilize COFs, an approach that is not widely used in the United States. Specifically, the researchers mechanochemically hybridize COFs with various functional materials to create unique heterostructures and hierarchical COFs to create desired hierarchical porosity.

They investigate the resultant COFs for radionuclide sequestration, with clear structure-function correlations and in-depth elucidation of the underlying mechanism. To enable the precision mechanosynthesis of COFs, the researchers unravel the mechanism of mechanochemical COF formation via combined experimental and computational tools, including ex-situ kinetic studies, in-situ probes, and computational simulations.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.