This patent disclosure includes a process that uniquely and unexpectedly results in the production of extremely high specific surface area and large pore volume carbon nanomaterial with high content of sp2 hybridized carbon-carbon in the form of nanosheets from a renewable carbonaceous raw material. The resulting nanomaterial is in particulate form or porous nanomaterial or dispersed in solvent. This process can also be used to produce carbon nanosheet on substrates or form a nanocomposite with other materials that results in exceptional properties.