This study investigates the thermal properties of isotopically engineered graphene, focusing on the impact of carbon isotope composition on its thermal conductivity. The researchers synthesized graphene with varying percentages of ${}^{13}\text{C}$ using chemical vapor deposition (CVD) and employed the optothermal Raman technique to measure the thermal conductivity. They found that isotopically pure ${}^{12}\text{C}$ (0.01% ${}^{13}\text{C}$) graphene exhibited a thermal conductivity of over 4000 W/mK at a measured temperature of 320 K, which is more than twice that of graphene with a 50%-50% mixture of ${}^{12}\text{C}$ and ${}^{13}\text{C}$. The results were consistent with molecular dynamics (MD) simulations corrected for long-wavelength phonon contributions using the Klemens model. The study highlights the importance of isotope effects in understanding thermal transport in two-dimensional crystals and provides valuable data for further research.This study investigates the thermal properties of isotopically engineered graphene, focusing on the impact of carbon isotope composition on its thermal conductivity. The researchers synthesized graphene with varying percentages of ${}^{13}\text{C}$ using chemical vapor deposition (CVD) and employed the optothermal Raman technique to measure the thermal conductivity. They found that isotopically pure ${}^{12}\text{C}$ (0.01% ${}^{13}\text{C}$) graphene exhibited a thermal conductivity of over 4000 W/mK at a measured temperature of 320 K, which is more than twice that of graphene with a 50%-50% mixture of ${}^{12}\text{C}$ and ${}^{13}\text{C}$. The results were consistent with molecular dynamics (MD) simulations corrected for long-wavelength phonon contributions using the Klemens model. The study highlights the importance of isotope effects in understanding thermal transport in two-dimensional crystals and provides valuable data for further research.