Improving the revenue of lignin conversion into carbon dots by prior amino modification

The conversion of lignin into carbon dots is an emerging technology to make use of this renewable and abundant material. The low yield and low quantum yield of carbon dots from lignin remain key challenges of this technique. Here, prior amino modification of lignin using the Mannich reaction was proposed to improve carbon dot production from lignin by the hydrothermal method. Accordingly, the yield and quantum yield of carbon dots were synchronously improved from 9.8 wt% and 5.36% to 68 wt% and to 42.7%, respectively, because modified lignin suppresses hydrochar formation. A survey of the impact of the lignin structure on carbon dot production, and the structure and property relationship of the as-prepared carbon dots showed that the process could make use of condensed lignin to produce carbon dots with high performance. Techno-economic analysis suggested that this process noticeably reduced the product selling price because of the improved yield. This study provides a strategy to reduce the production cost of carbon dots from lignin, which may inspire the community to extract money out of lignin.