Heng Zeng

Efficiently separating acetylene (C ₂ H ₂ ) from carbon dioxide (CO ₂ ) has been a long‐standing challenge due to their similar molecular dimensions and physical properties. Herein, we report a series of isostructural pillar‐layered metal–organic frameworks (MOFs), named JNU‐13, JNU‐13‐CH ₃ , and JNU‐13‐(CH ₃ ) ₂ . These MOFs feature one‐dimensional (1D) channels integrated with orthogonally arrayed side pockets, enabling dense packing of C ₂ H ₂ molecules while maintaining rapid diffusion pathways. Specifically, JNU‐13‐CH ₃ achieves a high C ₂ H ₂ packing density of 360 g L ⁻¹ , a low adsorption enthalpy of 31.61 kJ mol ⁻¹ , and adsorption/desorption coefficients one to two orders of magnitude higher than other benchmark MOFs. Breakthrough experiments reveal a high C ₂ H ₂ capture capacity of 3.46 mmol g ⁻¹ from an equimolar C ₂ H ₂ /CO ₂ mixture at 298 K and 1 bar, even under humid conditions. Moreover, we demonstrate the scale‐up synthesis of JNU‐13‐CH ₃ and gas‐cylinder collection of high‐purity C ₂ H ₂ , achieving >99.9% from a C ₂ H ₂ /CO ₂ (95/5) mixture and >99.7% from a C ₂ H ₂ /CO ₂ /CH ₄ (95/2.5/2.5) mixture. Overall, this study highlights the effectiveness of orthogonal‐arrayed side pockets for balancing dense packing and mass transport, offering a promising strategy for energy‐efficient C ₂ H ₂ purification.

Efficiently separating acetylene (C ₂ H ₂ ) from carbon dioxide (CO ₂ ) has been a long‐standing challenge due to their similar molecular dimensions and physical properties. Herein, we report a series of isostructural pillar‐layered metal–organic frameworks (MOFs), named JNU‐13, JNU‐13‐CH ₃ , and JNU‐13‐(CH ₃ ) ₂ . These MOFs feature one‐dimensional (1D) channels integrated with orthogonally arrayed side pockets, enabling dense packing of C ₂ H ₂ molecules while maintaining rapid diffusion pathways. Specifically, JNU‐13‐CH ₃ achieves a high C ₂ H ₂ packing density of 360 g L ⁻¹ , a low adsorption enthalpy of 31.61 kJ mol ⁻¹ , and adsorption/desorption coefficients one to two orders of magnitude higher than other benchmark MOFs. Breakthrough experiments reveal a high C ₂ H ₂ capture capacity of 3.46 mmol g ⁻¹ from an equimolar C ₂ H ₂ /CO ₂ mixture at 298 K and 1 bar, even under humid conditions. Moreover, we demonstrate the scale‐up synthesis of JNU‐13‐CH ₃ and gas‐cylinder collection of high‐purity C ₂ H ₂ , achieving >99.9% from a C ₂ H ₂ /CO ₂ (95/5) mixture and >99.7% from a C ₂ H ₂ /CO ₂ /CH ₄ (95/2.5/2.5) mixture. Overall, this study highlights the effectiveness of orthogonal‐arrayed side pockets for balancing dense packing and mass transport, offering a promising strategy for energy‐efficient C ₂ H ₂ purification.

C₃H₆ is a crucial building block for many chemicals, yet separating it from other C₃ hydrocarbons presents a significant challenge. Herein, we report a hydrolytically stable Cu₄I₄-triazolate metal-organic framework (MOF) (JNU-9-CH₃) featuring 1D channels decorated with readily accessible iodine and nitrogen atoms from Cu₄I₄ clusters and triazolate linkers, respectively. The exposed iodine and nitrogen atoms allow for cooperative binding of C₃ hydrocarbons, as evidenced by in situ single-crystal crystallography and Raman spectroscopy studies. As a result, JNU-9-CH₃ exhibits substantially stronger binding affinity for C₃H₄, CH₂═C═CH₂, and C₃H₈ than that for C₃H₆. Breakthrough experiments confirm its ability to directly separate C₃H₆ (≥99.99%) from C₃H₄/CH₂═C═CH₂/C₃H₈/C₃H₆ mixtures at varying ratios and flow rates. Overall, we illustrate the cooperative binding of C₃ hydrocarbons in a Cu₄I₄-triazolate MOF and its highly efficient C₃H₆ purification from quaternary C₃ mixtures. The study highlights the potential of MOF adsorbents with metal-iodide clusters for cooperative bindings and hydrocarbon separations.

Adsorptive separation employing porous materials is one of the most promising alternative technologies for C₂H₂ purification due to its energy-efficient and environmentally friendly advantages. Herein, we present the design and synthesis of a dicopper-paddle-wheel-based metal-organic framework (termed JNU-5-Me) with a carboxylate-azolate organic linker. The use of such a linker results in the axial positions of the dicopper paddle wheels being occupied by azolates, and therefore, a much-improved chemical stability of the framework structure. JNU-5-Me shows negligible adsorption of C₂H₄, C₂H₆, and CO₂ at 1.0 bar and 298 K, while a gate-opening effect for C₂H₂ and a large C₂H₂ adsorption (4.7 mmol g^-1) at 1.0 bar and 298 K. Dynamic breakthrough studies on JNU-5-Me demonstrate its excellent C₂H₂ separation performance from C₂H₂/CO₂ (50/50, v/v) and C₂H₂/CO₂/C₂H₄/C₂H₆ (70/10/10/10, v/v/v/v) mixtures. Additionally, in-situ infrared spectroscopy and Grand canonical Monte Carlo (GCMC) simulation reveal that the carboxylate oxygens and methyl groups on the framework are involved in the strong binding of C₂H₂, which may be attributed to the gate-opening effect of JNU-5-Me.

A linker methylation strategy to tune the pore size and surface electrostatic potential, rendering JNU-6-CH ₃ capable of directly separating high-purity C ₂ H ₄ from C ₂ H ₆ /C ₂ H ₄ mixtures with benchmark separation capacity under dry or humid conditions.

Energy-efficient hydrocarbon separation is of great significance. In this perspective, we discuss three main strategies in the design of MOF materials for hydrocarbon separation: surface engineering, molecular docking, and size exclusion.

The industrial separation of C ₂ H ₂ /CO ₂ is an energy-intensive process due to their similar molecular shapes. Here we demonstrate an ato-topology MOF with not only large C ₂ H ₂ adsorption capacity but also high C ₂ H ₂ /CO ₂ selectivity.

C₂H₂/CO₂separation is a challenging industrial process. We report a microporous MOF (JNU-4a) with square-planar mononuclear copper(ii) centers, allowing for a record high C₂H₂capture capacity from an equimolar C₂H₂/CO₂mixture.

Rigid molecular sieving materials work well for small molecules with the complete exclusion of large ones1-3, and molecules with matching physiochemical properties may be separated using dynamic molecular sieving materials4-6. Metal-organic frameworks (MOFs)7-9 are known for their precise control of structures and functions on a molecular level10-15. However, the rational design of local flexibility in the MOF framework for dynamic molecular sieving remains difficult and challenging. Here we report a MOF material (JNU-3a) featuring one-dimension channels with embedded molecular pockets opening to propylene (C3H6) and propane (C3H8) at substantially different pressures. The dynamic nature of the pockets is revealed by single-crystal-to-single-crystal transformation upon exposure of JNU-3a to an atmosphere of C3H6 or C3H8. Breakthrough experiments demonstrate that JNU-3a can realize high-purity C3H6 (≥99.5%) in a single adsorption-desorption cycle from an equimolar C3H6/C3H8 mixture over a broad range of flow rates, with a maximum C3H6 productivity of 53.5 litres per kilogram. The underlying separation mechanism-orthogonal-array dynamic molecular sieving-enables both large separation capacity and fast adsorption-desorption kinetics. This work presents a next-generation sieving material design that has potential for applications in adsorptive separation.