Converting CO2 with various epoxides to cyclic carbonates is extremely important. However, most of catalysts for such conversion either require complicated fabrication or are obtained from unsustainable sources. Motivated by this problem, we prepare biomass-based “all-in-one” carbon dots as nano-organocatalysts for firstly converting CO2 to cyclic carbonates. In this work, carbon dots (CD@KI) with high catalytic performance and good recyclability are prepared from sodium phytate (SP), polyethylenimine (PEI) and KI using one-pot hydrothermal treatment featuring cheap precursors and simple operation. Assisted by highly catalytic activity of CD@KI, up to 99.5% yield is achieved for converting CO2 and various epoxides to cyclic carbonates under mild conditions (solvent-free and 1 atm of CO2). Moreover, the conversion yield is maintained for reactions up to ten grams in scale. Significantly, by taking advantage of the inherent luminescence of CD@KI, the as-formed cyclic carbonates catalyzed by CD@KI can be directly converted to afterglow polymer composites.