High Working Capacity Acetylene Storage at Ambient Temperature Enabled by a Switching Adsorbent Layered Material

Unlike most gases, acetylene storage is a challenge because of its inherent pressure sensitivity. Herein, a square lattice (sql) coordination network [Cu(4,4'-bipyridine)₂(BF₄)₂]_n (sql-1-Cu-BF₄) is investigated with respect to its C₂H₂ sorption behavior from 189 to 298 K. The C₂H₂ sorption studies revealed that sql-1-Cu-BF₄ exhibits multistep isotherms that are temperature-dependent and consistent with the transformation from "closed" (nonporous) to four "open" (porous) phases induced by the C₂H₂ uptake. The Clausius-Clapeyron equation was used to calculate the performance of sql-1-Cu-BF₄ for C₂H₂ storage at pressures >1 bar, which revealed that its volumetric working capacity at 288 K is slightly superior to acetone (174 vs 170 cm³ cm^-3) over a safer pressure range (1-3.5 vs 1-15 bar). Molecular simulations provided insights into the observed switching phenomena, revealing that the layer expansion of sql-1-Cu-BF₄ occurs via intercalation and inclusion of C₂H₂. These results indicate that switching adsorbent layered materials offer promise for utility in the context of C₂H₂ storage and delivery.