As-synthesized [Zn-2(Oxac) (Taz)(2)]center dot(H2O)(2.5), referred to as ZOTW(2.5), was prepared from aqueous methanol solutions of Zn-5(CO3)(2)(OH)(6) and two kinds of ligands of 1,2,4-triazole (Taz) and oxalic acid (Oxac) at 4S3 K for 12 h. The crystal structure was determined by the Rietveld method. As-synthesized ZOTW2.5 was pretreated at 383 K and 1 mPa for t(ph), ZOTW(x)(t(pt)h). ZOTW(x)(>= 3h) showed a type I adsorption isotherm for N-2 at 77 K having a saturation amount (V-s) of 180 mg/g, but that pretreated shortly showed only 1/10 in V-s CO2 was adsorbed at 303 K in sigmoid on nonporous ZOTW(x)(<= 2h) and in Langmuir-type on ZOTW(x)(>= 3h) to reach the adsorption amount of 120 mg/g at 700 Torr. N2 adsorption on ZOTW(x)(<= 2h)deCO(2), degassed after CO, adsorption on ZOTW(x)(<= 2h), was promoted 5-fold from 180 mg/g on ZOTW(x)(t(pt)h) and ZOTW(x)(>= 3h)deCO(2) up to ca. 1000 mg/g. The interaction of CO2 and H2O molecules in micropores may lead to a new route for mictopore formation.