Topology-Guided Design for Sc-soc-MOFs and Their Enhanced Storage and Separation for CO₂ and C₂-Hydrocarbons

Evaluating the effect of ligand substitution on metal ions and/or clusters during the MOF growth process is conducive to rational design of isoreticular MOFs with improved performance. Through topological direction and ligand substitution strategy, we herein constructed two Sc-soc-MOFs (Sc-EBTC and Sc-ABTC) based on two similar rectangular-planar diisophthalate ligands, linear-shaped H₄EBTC (1,1'-ethynebenzene-3,3',5,5'-tetracarboxylic acid) and zigzag-shaped H₄ABTC (3,3',5,5'-azobenzenetetracarboxylic acid), under solvothermal conditions with formic acid as a modulator. {Sc[(Sc₃O)(H₂O)₃]₃(EBTC)₆} (Sc-EBTC) possesses two distinct clusters as SBUs, trinuclear [Sc₃O(CO₂)₆] (SBU1) and mononuclear cluster [ScO₆] (SBU2), which maintain the soc-topology except for the mononuclear [ScO₆] instead of the corresponding trinuclear [Sc₃O(CO₂)₆] in Sc-ABTC ({(Sc₃O)(H₂O)₃(ABTC)_1.5(NO₃)}). Notably, Sc-EBTC represents a rare soc-MOF with two distinct clusters as SBUs. Due to similar pore spaces, the two Sc-soc-MOF materials both exhibit enhanced and comparable gas sorption and selectivity performances. Specially, their remarkable C₂H₂, C₂H₄, and CO₂ storage capacity along with prominent CO₂/CH₄ and C₂-hydrocarbons/CH₄ separations indicate that these Sc-soc-MOFs are promising adsorbents for natural gas purification under ambient conditions.