The present invention provides a metal-carbon composite of a core-shell structure and a method of synthesizing the same. The method includes preparing a first polymer-covered glass substrate with a nano-thickness metal film deposited thereon; immersing the first polymer-covered glass substrate with the metal film to delaminate one or more 2D freestanding organic-metal nanosheets from the first polymer-covered glass substrate; transferring the one or more 2D freestanding organic-metal nanosheets onto a second target substrate; and annealing the one or more 2D freestanding organic-metal nanosheets to decompose an organic portion of the organic-metal nanosheet into an amorphous carbon-containing shell forming a metal-carbon nanocomposite of a core-shell structure.