Guest transport through discrete voids (closed pores) in crystalline solids is poorly understood. Herein, we report the gas sorption properties of a nonporous coordination network, {[Co(bib) 2 Cl 2 ] ⋅ 2MeOH} n ( sql‐bib‐Co‐Cl‐α ), featuring square lattice ( sql ) topology and the bent linker 1,3‐bis(1 H ‐imidazol‐1‐yl)benzene (bib). The as‐synthesized sql‐bib‐Co‐Cl‐α has 11.3 % (313 Å 3 ) of its unit cell volume in closed pores occupied by methanol (MeOH). Upon desolvation and air exposure, sql‐bib‐Co‐Cl‐α underwent a single‐crystal to single‐crystal (SC‐SC) phase transformation to sql‐bib‐Co‐Cl‐β′ , wherein MeOH was replaced by water. Activation (vacuum or N 2 flow) resulted in dehydration and retention of the closed pores, affording sql‐bib‐Co‐Cl‐β with 7.7 % (194 Å 3 ) guest‐accessible space. sql‐bib‐Co‐Cl‐β was found to preferentially adsorb C 2 H 2 (at 265 K) over CO 2 (at 195 K) through gate‐opening mechanisms, at gate‐opening pressures of 59.8 and 27.7 kPa, respectively, while other C2 gases were excluded. PXRD was used to monitor transformations between the three phases of sql‐bib‐Co‐Cl , while in situ DSC, in situ SCXRD under CO 2 pressure, and computational studies provided insight into the guest transport mechanism, which we attribute to the angular, flexible nature of the bib ligand. Further, the preferential adsorption of C 2 H 2 over CO 2 and other C2 gases suggests that transiently porous sorbents might have utility in separations.