1 Department of Chemical and Materials Engineering, and Centre for NanoScience Research (CeNSR), Concordia University, 7141 Sherbrooke Street West., Montreal, Quebec H4B 1R6, Canada.
2 Department of Physics, and Centre for NanoScience Research (CeNSR), Concordia University, 7141 Sherbrooke Street West., Montreal, Quebec H4B 1R6, Canada.
3 Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
4 Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
5 Center for Two-Dimensional and Layered Materials, and Centre for Atomically Thin Multifunctional Coatings, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
6 Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16082, United States.
7 Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16082, United States.
8 Graduate Program in Physics, Federal University of Piauí, 64049550 Teresina, PI, Brazil.
9 Graduate Program in Engineering and Materials Science, Federal University of Piauí, 64049550 Teresina, PI, Brazil.

Coal, historically a low-cost and abundant energy resource, is emerging as a promising carbon-rich precursor for advanced nanomaterials. In this work, we introduce a reductive intercalation strategy to synthesize reduced (electron-rich) graphene quantum dots (GQDs) directly from anthracite coal. Potassium intercalation transforms the rigid graphenic framework of anthracite coal into a stage-I polyelectrolyte salt that spontaneously dissolves in N-methyl-2-pyrrolidone (NMP), yielding uniform (2.5-3.5 nm), reduced GQDs without the need for sonication or oxidative processing. The method achieves an isolated yield of <28% based on the starting mass of anthracite coal. Practically, this means that 3.6 kg of coal can yield up to 1 kg of graphene quantum dots, highlighting the scalability and efficiency of this approach. The resulting GQDs exhibit a direct bandgap of 3.4 eV and strong excitation-dependent photoluminescence. Thermo-optical characterization of GQDs in NMP reveals a thermal diffusivity of (6.4 ± 0.3) × 10^-8 m²/s and a nonlinear refractive index of -4.69 × 10^-9 cm²/W, demonstrating their potential for photothermal conversion and nonlinear optical applications. Notably, the GQDs can be precipitated and collected as slurries or powders that are readily dispersible in a variety of other solvents, including water, ethanol, isopropanol, facilitating their integration into diverse solution-processable systems. This scalable, oxidation-free approach positions coal as a viable feedstock for high-performance quantum nanomaterials with potential applications in sustainable sensing, and thermal management technologies.