Topology Reconfiguration of Anion-Pillared Metal-Organic Framework from Flexibility to Rigidity for Enhanced Acetylene Separation

A Rigid, Stable, and Scalable Aliphatic MOF Adsorbent for Efficient C2H2/CO2 Separation with Record Acetylene Packing Density

Integrating separation parameters such as high adsorption capacity and selectivity, moderate adsorption enthalpy (Qst), along with industrial factors including cyclic stability, cost-effectiveness, and scalability into a single adsorbent remains highly challenging due to inherent trade-offs among these properties. Herein, we strategically leverage the coordination modes of aliphatic ligands to significantly enhance C2H2/CO2 separation performance. The structure flexibility and pore metrics are finely modulated by hydroxylated aliphatic acid (DLmal). As a result, the rigid Zn-bpy-DLmal exhibits an exceptional C2H2 adsorption capacity of 1.4 mmol g-1 at 0.01 bar, high C2H2/CO2 selectivity (49), and moderate C2H2 Qst value (38.4 kJ mol-1). Notably, it achieves record-high C2H2 packing densities of 347 g L-1 at 0.01 bar and 747 g L-1 at 0.5 bar. Furthermore, the scale-up production of Zn-bpy-DLmal to kilogram quantities has been successfully achieved at an estimated cost of $74 per kilogram. Dynamic breakthrough experiments confirm its practical C2H2/CO2 separation performance with excellent cyclability under high flow rates and both dry and humid conditions. Moreover, two-bed pressure swing adsorption simulations demonstrate a high-purity C2H2 (>99%) yield of 14.64 mol with a recovery of 88.2% per cycle.

Electrostatic Potential Matching in an Anion-Pillared Framework for Benchmark Hexafluoroethane Purification from Ternary Mixture

One-step purification of CF3CF3 from ternary CF3CH2F/CF3CHF2/CF3CF3 mixture is crucial since its vital role in the semiconductor industry. However, efficient separation of chemically inert CF₃CF₃ remains challenging due to the difficulty in creating specific recognition sites in porous materials. In this work, we report the first example of anion-pillared MOFs to the separation of fluorinated electronic specialty gases, utilizing the unique electrostatic potential matching in the bipolar pores of SIFSIX-1-Cu to realize a benchmark CF3CH2F/CF3CHF2/CF3CF3 separation. SIFSIX-1-Cu exhibits the highest CF3CH2F and CF3CHF2 adsorption capacity at 0.01 bar, as well as the highest CF3CH2F/CF3CF3 and CF3CHF2/CF3CF3 IAST selectivity. Additionally, high-purity (≥ 99.995%) CF3CF3 with record productivity (882.9 L kg-1) can be acquired through one-step breakthrough experiment of CF3CH2F/CF3CHF2/CF3CF3 (5/5/90). Theoretical calculations further reveal that the coexistence of electronegative SiF6 2- and partially electropositive H sites promotes SIFSIX-1-Cu to effectively anchor CF3CH2F and CF3CHF2 through multiple supramolecular interactions.

A Scalable Pore-space-partitioned Metal-organic Framework Powered by Polycatenation Strategy for Efficient Acetylene Purification

Efficient separation of acetylene (C2H2) from carbon dioxide (CO2) and ethylene (C2H4) is a significant challenge in the petrochemical industry due to their similar physicochemical properties. Pore space partition (PSP) has shown promise in enhancing gas adsorption capacity and selectivity by reducing pore size and increasing the density of guest binding sites. Herein, we firstly employ the 2D→3D polycatenation strategy to construct a PSP metal-organic framework (MOF) Ni-dcpp-bpy, incorporating functional N/O sites to enhance C2H2 purification. The polycatenated framework with optimized pore size and regularity, exhibiting significant improvements over traditional PSP MOFs by resolving the critical contradiction of balancing C2H2 uptake (98.5 cm3 g-1 at 298 K, 100 kPa) and selectivity of C2H2/CO2 (3.4), C2H2/C2H4 (5.9), and C2H2/CH4 (96.4) in a MOF. Breakthrough experiments confirm high-purity C2H4 (>99.9 %) and high C2H2 productivity from binary and ternary mixtures. Notably, Ni-dcpp-bpy exhibits excellent water stability, scalability, and regenerability after 20 cycles for separating C2H2/CO2. Theoretical calculations verify that the strong binding of C2H2 is mainly attributed to the C-H⋅⋅⋅O/N interactions between host Ni-dcpp-bpy and guest C2H2 molecules. The polycatenation strategy not only improved industrial C2H2 purification efficiency but also enriched the design diversity of customized MOFs for other gas separation applications.

Freeze-Cast MIL-53(Al) Porous Materials with High Thermal Insulation and Flame Retardant Properties

The development of materials with superior thermal insulation and flame retardancy is critical for industrial applications and daily life. Metal-organic framework (MOF)@poly(vinyl alcohol) (PVA) (MOF@PVA) aerogel composites have demonstrated remarkable thermal insulation and flame retardancy properties. In this work, MIL-53(Al) was directly mixed with PVA and formed by freeze-drying, and the influence of the pore structure on the thermal insulation and flame retardancy properties of the materials was investigated. The incorporated MIL-53(Al) nanoparticles introduced abundant micro- and mesopores, enhancing the complexity of the pore structure and improving the thermal insulation and flame retardancy properties of the aerogels. The directionally freeze-cast aerogel achieved a thermal conductivity of 0.040 W·mK-1, and maintained excellent thermal insulation ability even at 220 °C. Furthermore, the aerogel exhibited nonflammable and self-extinguishing characteristics. This environmentally friendly manufacturing method provides new ideas for the design of MOF-based composites, thereby expanding their application areas.