We report new microporous metal-organic 3D coordinated copolymers that exhibit both highly efficient gas adsorption capability and high temporal stability. The Zn-coordinated copolymers (MBCn) were prepared by mixing two organic ligands at various molar ratios: the widely used benzenedicarboxylate (BDC) and its analogous Cn-acid with non-polar alkoxy side chains of various lengths. All MBCn copolymers bearing alkoxy side chains exhibited identical framework structures to that of MOF-5 prepared with only the BDC ligand. Interestingly, compared to MOF-5, MBCn copolymers exhibited up to three times higher gas adsorption properties and higher temporal structural stability. Therefore, copolymerization with organic ligands bearing alkoxy side chains is a promising strategy for the development of new microporous metal-organic hybrid materials.