The advances in C-H bond activation enable new synthetic routes for functional chemicals. Since C-H bonds are thermodynamically stable, many catalysts have been developed for C-H activation, including transition metals (e.g., palladium, cobalt, and gold), zeolites, and metal-organic frameworks.

While previous research focused on C-H activation in short-chain alkanes (e.g., methane and ethane) and aromatic compounds, C-H activation in long-chain organic molecules is rarely reported. Yet, breaking C-H bonds in these complex compounds is an important step for recycling plastics and other organic wastes, which has significant potential in transforming environmental pollutants into more valuable chemicals.

Here, we discovered that C-H activation in long-chain molecules can be facilely enabled by light and 2D materials. As shown in Figure 1, by putting organic molecules (e.g., cetyltrimethylammonium chloride, polyethylene) on a monolayer transition metal dichalcogenide, such as WSe2, WS2, or MoS2, we can use low-power laser to convert these compounds into bright carbon dots. This process involves the WSe₂-mediated C-H activation followed by subsequent C=C bond formation.

Through a combination of experimental and theoretical investigations, we discovered that defects and oxidized states on the surfaces of 2D TMDCs play a crucial role in promoting the adsorption of hydrogen and lowering the energy barriers for the critical C-C coupling step, which is essential for activating the C-H bonds in long-chain molecules.

Remarkably, we found that 2D TMDCs outperformed traditional metal catalysts in driving these transformations. This light-driven, 2D-mediated approach can also yield functional carbon dots with strong light emission for data encryption and information storage applications.

Moving forward, we envision that this 2D TMDC-mediated light-driven C-H activation in complex organic molecules will enable new applications in chemical synthesis, photonics, degradation of organic pollutants, and plastic recycling.