Ultramicroporous Metal‐Organic Frameworks Functionalized With Acyclic Ether Oxygen Bonds for Efficient C ₂ H ₂ /CO ₂ and C ₂ H ₂ /C ₂ H ₄ Separation

ABSTRACT Designing and tailoring porous materials to realize the precise separation of C 2 H 2 , C 2 H 4 and CO 2 with nearly identical kinetic diameters is an extremely challenging research task. In this study, a novel microporous metal‐organic framework (MOF) designated UPC‐523 (Zn 3 (H 4 edda) 2 ·DMF) has been synthesized by employing 5,5'‐(ethane‐1,2‐diylbis(oxy))diisophthalic acid (H 4 edda), which is constructed with ethylene ether linkages (‐O‐CH 2 ‐CH 2 ‐O‐). This rational design strategy employs ethylene ether moieties to construct a highly electronegative pore microenvironment within the framework. UPC‐523 is endowed with abundant electronegative sites, the uncoordinated oxygen atoms in the confined pores selectively capture C 2 H 2 from CO 2 and C 2 H 4 through hydrogen‐bonding interactions, enabling it to achieve selective adsorption of C 2 H 2 . At 298 K and 100 kPa, this MOF exhibits a C 2 H 2 adsorption capacity of 44.9 cm 3 /g, coupled with a moderate isosteric heat of C 2 H 2 adsorption ( Q st ) of 33.7 kJ/mol, a property conducive to the direct desorption and regeneration of UPC‐523. The IAST selectivities of C 2 H 2 /C 2 H 4 (v/v = 50/50) and C 2 H 2 /CO 2 (v/v = 50/50) are 2.1 and 3.4, respectively, comparable to the majority of reported MOFs under identical conditions. Dynamic breakthrough experiments reveal that UPC‐523 can efficiently separate C 2 H 2 from C 2 H 2 /CO 2 or C 2 H 2 /C 2 H 4 mixtures.