Solvent-linked porous covalent organic polymers (COPs) and a method of preparing the same are described. The porous covalent organic polymers are linked by a solvent and are thus suitable for the transportation and storage of natural gas. A method of preparing the porous covalent organic polymers by conducting alkylation polymerization between an aromatic monomer and a chlorine-based solvent in the presence of a Lewis acid catalyst is described. Porous stretchable covalent organic polymers having pores with various sizes can be synthesized simply and quickly at room temperature and atmospheric pressure without a heating or purification step. The covalent organic polymers have very high natural gas storage capacity due to the flexible porous network structure thereof and thus are suitable for storage and transportation of natural gas and useful as a natural gas adsorbent.