 New multilayered microcapsules have been synthesized for thermal energy storage applications.  The thermal conductivity of the synthesized microcapsules is increased with a second layer.  The study was carried out in accordance with the principles of green chemistry.Nowadays, research and development of phase change materials (PCMs) become popular parallel with the increased importance of thermal energy storage (TES). In this study, n-heptadecane was encapsulated via natural mineral shell magnesium carbonate (MgCO3) and these capsules were coated with silver to enhance the thermal conductivities of capsules. Microcapsules were synthesized by self-assembly method (Figure A). The thermal, physical and chemical properties of MgCO3 and MgCO3@Ag capsules were compared.The morphologies of capsules are seen as bar-shaped. The latent heat capacities of capsules are compatible with the literature while remaining the phase change temperature range. The thermal conductivities of MgCO3@Ag capsules were found higher than MgCO3 capsules at four times. The results show that these new capsules candidates can be used for TES building applications. Figure A. Reaction FlowchartPurpose: In this study, attention was paid to the selection of materials used at every stage in the production of microencapsulated FDM by paying attention to green chemistry principles, to give priority to recycling materials, and to carry out microencapsulation processes at lower temperatures and in a short time. The properties of the developed new microencapsulated PCMs have been determined so that they can be used in various heating and cooling applications. Theory and Methods:Microcapsules were synthesized by self-assembly method (Figure A). Results:Material synthesis was carried out in an efficient and environmentally friendly manner. All thermal tests and characterizations of the obtained microcapsules were performed. Conclusion:In this research, encapsulation of n-heptadecane, one of the organic phase change materials, with minerals found in nature that can be used in different thermal energy storage applications, cheap, in a short time and with less energy consumption, was carried out by considering the principles of green chemistry. Material synthesis was carried out in an efficient and environmentally friendly manner. All thermal tests and characterizations of the obtained microcapsules were performed.