Seawater desalination is vital to our modern civilization. Here, we report that the carbon honeycomb (CHC) has an outstanding water permeability and salt rejection in seawater desalination, as revealed by molecular dynamics simulations. More than 92% of ions are rejected CHC at applied pressures ranging from 50 250 MPa. a perfect below 150 Mpa. On increasing pressure up MPa, reduces only 92%. P...