The construction of superstable metal–organic frameworks (MOFs) for selective gas uptake is urgently demanded but remains a great challenge. Herein, a unique bifunctional deformed [Ga3O­(COO)6] inorganic secondary building unit (SBU) generated from the desymmetrical evolution of typical triangular prismatic trinuclear cluster was first introduced, which was extended by an isosceles triangular organic linker to produce a robust Ga-MOF (SNNU-63). Remarkably, SNNU-63 can stabilize in water at 25 °C for 96 h and at 80 °C for more than 24 h, which surpasses nearly all other Ga-MOFs. The combined effects of open metal sites and hydrophobic pore environment provided by deformed [Ga3O] SBUs render SNNU-63 with high C2H2 storage capacity and efficient C2H2 and natural gas purification performance. The ideal adsorbed solution theory calculation, column breakthrough tests, and grand canonical Monte Carlo simulations demonstrate that SNNU-63 is a potential material for addressing the challenge of C2H2/CO2 and C2H2/CH4 mixture separation under ambient conditions.

Acetylene (C 2 H 2 ) purification is of great importance for many chemical synthesis and processes. Metal−organic frameworks (MOFs) are widely used for gas adsorption and separation due to their variable structure and porosity. However, the exploitation of ideal MOF adsorbents for C 2 H 2 keeps a challenging task. Herein, a combination of open metal sites (OMSs) and Lewis basic sites (LBSs) in robust MOFs is demonstrated to effectively promote the C 2 H 2 purification performance. Accordingly, SNNU-37(Fe/Sc), two isostructural MOFs constituted by [Fe 3 O(COO) 6 ] or [Sc 3 O(COO) 6 ] trinuclear clusters and amide-functionalized tricarboxylate linkers, were designed with extra-stable 3,6-connected new architectures. Derived from the coexistence of high-density OMSs and LBSs, the C 2 H 2 adsorption amounts of SNNU-37(Fe/Sc) are much higher than those values for C 2 H 4 and CO 2 . Theoretical IAST selectivity values of SNNU-37(Fe) are 2.4 for C 2 H 2 /C 2 H 4 (50/50, v/v) and 9.9 for C 2 H 2 /CO 2 (50/50, v/v) at 298 K and 1 bar, indicating an excellent C 2 H 2 separation ability. Experimental breakthrough curves also revealed that SNNU-37(Fe) could effectively separate C 2 H 2 /C 2 H 4 and C 2 H 2 /CO 2 under ambient conditions. GCMC simulations further indicate that open Fe or Sc sites and amide groups mainly contribute to stronger adsorption sites for C 2 H 2 molecules.