Isoreticular Contraction of Cage-like Metal–Organic Frameworks with Optimized Pore Space for Enhanced C₂H₂/CO₂ and C₂H₂/C₂H₄ Separations

Abstract

The C 2 H 2 separation from CO 2 and C 2 H 4 is of great importance yet highly challenging in the petrochemical industry, owing to their similar physical and chemical properties. Herein, the pore nanospace engineering of cage-like mixed-ligand MFOF-1 has been accomplished via contracting the size of the pyridine-and carboxylic acid-functionalized linkers and introducing a fluoride-and sulfate-bridging cobalt cluster, based on a reticular chemistry strategy. Compared with the prototypical MFOF-1, the constructed FJUT-1 with the same topology presents significantly improved C 2 H 2 adsorption capacity, and selective C 2 H 2 separation performance due to the reduced cage cavity size, functionalized pore surface, and appropriate pore volume. The introduction of fluoride-and sulfate-bridging cubane-type tetranuclear cobalt clusters bestows FJUT-1 with exceptional chemical stability under harsh conditions while providing multiple potential C 2 H 2 binding sites, thus rendering the adequate ability for practical C 2 H 2 separation application as confirmed by the dynamic breakthrough experiments under dry and humid conditions. Additionally, the distinct binding mechanism is suggested by theoretical calculations in which the multiple supramolecular interactions involving C−H•••O, C−H•••F, and other van der Waals forces play a critical role in the selective C 2 H 2 separation.

Metal–Organic Framework with Space-Partition Pores by Fluorinated Anions for Benchmark C2H2/CO2 Separation

“…Metal–organic frameworks (MOFs) provide exceptional porosity and allow precise tuning of pore characteristics, making them a promising new category of adsorbents for gas storage and separation. − Among gas separations, the C 2 H 2 /CO 2 separation stands out as exceptionally challenging, largely owing to their similar kinetic molecular size (3.3 Å). − Since the groundbreaking achievement of the pioneering MOF designed for C 2 H 2 /CO 2 separation in 2005, numerous MOF materials have been developed to showcase effective separation through pore size tuning and surface functionalization. − Particularly, pore space partition (PSP) has been extensively developed as a powerful strategy to afford benchmark C 2 H 2 /CO 2 separation performance by dramatically increasing the number of host–guest binding sites (Scheme a). − Generally, PSP entails partitioning large pore space into smaller pores to boost the adsorption site density . It can also improve the framework stability.…”

Three Polyhedron-Based Metal–Organic Frameworks Exhibiting Excellent Acetylene Selective Adsorption

“…Therefore, the separation of C 2 H 2 from C 2 H 6 /C 2 H 4 /C 2 H 2 mixtures is a crucial and challenging task . Current technology for recovering C 2 H 2 from other gases generally relies on cryogenic distillation or solvent extraction, which results in high energy consumption and negative environmental impact. , In recent years, adsorptive separation technology based on porous materials has been considered a promising feasibility method, which has the advantages of energy saving, environmental benefits, and high efficiency …”