NOVELTY - Preparing a porous organic polymer capable of adsorbing gas involves reacting a monomer with a Friedel-Crafts catalyst in an aprotic organic solvent and with formaldehyde dimethyl acetal (FDA), where the monomer:FDA molar ratio is comprised within the range of 1:9 to 1:30, preferably is of about 1:16.    USE - The methods are useful for preparing porous organic polymer capable of adsorbing gas; and for storing gas preferably selected from hydrogen, methane and carbon dioxide (all claimed).    ADVANTAGE - The porous organic polymer is capable of effectively adsorbing and storing gases such as carbon dioxide, hydrogen and methane; and is capable of being prepared by a method which makes use of consumer reagents and which is simple, cost-effective and easy to scale-up.    DETAILED DESCRIPTION - Preparing a porous organic polymer capable of adsorbing gas involves reacting a monomer of formula (I) with a Friedel-Crafts catalyst in an aprotic organic solvent and with formaldehyde dimethyl acetal (FDA), where the monomer of formula(I):FDA molar ratio is comprised within the range of 1:9 to 1:30, preferably is of about 1:16.    A=selected from a C atom, a Si atom, a Ge atom and a group of formula A; and    B', C', D and E=a 5-membered or 6-membered ring structure selected from the monovalent radicals of the compounds benzene, pyridine, pyran, cyclopentadiene, pyrrole, furan, thiophene and naphthalene, anthracene, phenanthrene, pyrene, optionally having one or more substituents selected from nitro, amino, hydroxyl, sulfonyl, halogen, phenyl, alkyl, haloalkyl, hydroxyalkyl, aminoalkyl, aryl, alkenyl, alkynyl, and heteroaryl groups.    INDEPENDENT CLAIMS are included for:    (1) a porous organic polymer capable of adsorbing gas having formula (II), comprising ultramicropores having pore size lower than 7 Angstrom ; and    (2) a method of storing a gas preferably selected from hydrogen, methane and carbon dioxide, which involves storing gas using porous organic polymer capable of adsorbing gas.    n=an integer.