Seunghyeon Kim

     In recent decades, visible light photocatalysis has enabled unprecedented transformations in organic synthesis, proving its utility in the pharmaceutical industry to synthesize drug-like compounds.  However, low energy efficiency of the synthetic protocols and the high cost of molecular photocatalysts hinder their large-scale applications. Therefore, I am eager to develop polymeric photocatalysts with high energy-efficiency, stability, and easy recovery to save light energy and reuse the photocatalysts.

     To develop such ideal photocatalysts, conjugated microporous polymers (CMPs) are promising candidates because their properties can be finely tuned for individual reactions, maximizing photocatalytic reactivity and stability. However, typically large size (> 1 μm) of CMPs could significantly limit their quantum yields because of poor substrate accessibility to excitons from the inner core of CMPs, making the core materials dormant for photocatalysis. To address this inefficient use of the materials and light energy, we recently proposed the concept of hairy CMP nanoparticles for their solvent-specific dispersibility and developed a simple and versatile dispersion polymerization protocol, which enables facile access to monodisperse hairy CMP nanoparticles with controlled size from 15 nm to 180 nm.  The precise control of size was crucial to reveal that smaller CMP nanoparticles achieve higher photocatalytic reactivity in various organic transformations.

     These recent studies successfully described the potential of hairy CMP nanoparticles for developing energy-efficient photocatalytic reactions, and also demonstrated broad applicability of the dispersion polymerization approach to other cross-coupling protocols. Encouraged by the versatility of the synthetic method, my research currently focuses on developing covalent organic framework (COF) nanoparticles to investigate the effects of crystallinity of the conjugated polymer network on the photocatalytic reactivity and stability of the nanoparticles. Apart from engineering the cores of hairy nanoparticles, I am also interested in decorating the hairs with stimuli-responsive or redox active functional groups to design external stimuli-controlled dual photocatalytic reactions or to achieve efficient cascade photocatalytic reactions at the surface of CMP nanoparticles.