Fe-Based Microporous Metal–Organic Framework for C₂H₂/CO₂ Separation

Acetylene (C₂H₂) is a crucial industrial feedstock, but its production typically yields CO₂-contaminated mixtures, posing a significant separation challenge. To overcome this critical separation challenge, we synthesized an iron-based metal-organic framework named STU-130 with a <b>brn-1</b> underlying net. It features a 1D channel (6.4 × 5.8 Ų) in the <i>a</i>-axis, which is decorated with uncoordinated carboxylate oxygen on the porous surface. These structural features enable STU-130 to preferentially adsorb C₂H₂ over CO₂ through differential host-guest interaction strengths. Single-component gas adsorption tests revealed a significant difference in uptake capacities between C₂H₂ (106.8 cm³ g^-1) and CO₂ (80.84 cm³ g^-1), with an IAST-predicted selectivity of 4.2 for equimolar C₂H₂/CO₂ mixtures (50:50, 298 K, and 1 bar). Dynamic breakthrough tests further confirmed the C₂H₂/CO₂ separation performance with the C₂H₂/CO₂ elution time gap of 25 min g^-1. Density functional theory calculations and grand canonical Monte Carlo simulations revealed that the uncoordinated carboxyl oxygen atoms can selectively bind C₂H₂ through strong C-H···O hydrogen bonds (32.6 kJ mol^-1), playing a pivotal role in C₂H₂/CO₂ selective separation.