Formation of a N/O/F-Rich and Rooflike Cluster-Based Highly Stable Cu(I/II)-MOF for Promising Pipeline Natural Gas Upgrading by the Recovery of Individual C3H8 and C2H6 Gases

Pore space partition on a sulfonate-rich metal-organic framework for purification of methane from natural gas

By implementing the pore space partition (PSP) strategy on a sulfonate-rich acs-type metal-organic framework (MOF), we developed a new pacs structure, which features segmented pores with abundant O/N interacting sites. This structure selectively uptakes C2H6 and C3H8 from the ternary mixture of C2H6/C3H8/CH4 with high selectivity and capacity, enabling effective purification of CH4 from natural gas through a single adsorption process.

Efficient One-Step Purification of Methanol-to-Olefin Products Using a Porphyrinyl MOF to Achieve Record C2H4 and C3H6 Productivity

The separation of methanol-to-olefin (MTO) products to obtain high-purity ethylene (C2H4) and propylene (C3H6) is a challenging yet critical task, as these compounds are essential industrial raw materials for polymer synthesis. However, developing adsorbents with high selectivity and productivity for C2H4/C3H6 remains a significant challenge and an urgent necessity. In this study, a porphyrinyl metal-organic framework (MOF), Al-TCPP, was developed for the simultaneous recovery of C3H6 and C2H4 through a one-step adsorption-desorption process. Benefiting from its well-developed microporous structure and abundant N- and O-accessible sites, Al-TCPP demonstrated exceptional adsorption capacities and selectivity for C3H6 and ethane (C2H6) over C2H4 under ambient conditions. The adsorption capacities (in cm3·g-1) reached 162.4 for C3H6 and 118.5 for C2H6 at 298 K and 100 kPa. The ideal adsorbed solution theory (IAST) selectivity values for C3H6/C2H4 and C2H6/C2H4 were 10.1 and 1.8, respectively. Thermodynamic studies and theoretical calculations revealed stronger interactions between C2H6 and C3H6 molecules with the Al-TCPP framework than with C2H4. Systematic breakthrough experiments demonstrated outstanding separation performance for binary C2H6/C2H4 and C3H6/C2H4 mixtures, as well as ternary C3H6/C2H6/C2H4 mixtures, achieving record productivities of 150.2 and 86.5 L·kg-1 for polymer-grade C2H4 (≥99.9%) and C3H6 (≥99.5%), respectively. Notably, the separation performance remained stable under variable flow rates, temperatures, humidities, and multiple adsorption-desorption cycles. Overall, this study highlighted Al-TCPP as a highly competitive adsorbent for addressing the challenges in MTO product separation. Moreover, it offered valuable insights into the design of MOFs with heteroatom-rich accessible sites for efficient separation of low-carbon hydrocarbons.

Methane Storage and Purification of Natural Gas in Metal-Organic Frameworks

Natural gas, primarily composed of methane (CH4), represent an excellent choice for a potentially sustainable renewable energy transition. However, the process of compressing and liquefying CH4 for transport and storage typically results in significant energy losses. In addition, in order to optimize its efficacy as a fuel, the CH4 content of natural gas needs to be increased to a level of at least 97 % to ensure its quality and efficiency in various applications. Metal-organic frameworks (MOFs) represent a novel category of porous materials that possess exceptional capability in modifying pore size and chemical environment, making them ideally suited for the storage of CH4 and the adsorption of propane (C3H8), ethane (C2H6), carbon dioxide (CO2), nitrogen (N2), and hydrogen sulfide (H2S) to facilitate the purification process of CH4 from natural gas. In this paper, we systematically summarize the mechanism by which MOF materials facilitate the storage of CH4 and the purification of CH4 from natural gas, leveraging the structural characteristics inherent to MOF materials. The focus of further research should also be directed towards the investigation of CH4 storage by flexible MOFs, the resolution of the trade-off dilemma, and the commercial application of MOFs.

Fabricating a Robust Ultramicroporous Metal-Organic Framework for Purifying Natural Gas and Coal Mine Methane

Purifying methane (CH4) from natural gas and coal mine methane (CMM) is of great significance but challenging in the chemical industry. Herein, a robust ultramicroporous metal-organic framework (MOF) is reported, which can be synthesized on a gram scale by stirring under room temperature. Single-component adsorption isotherms of gases (CH4, ethane (C2H6), propane (C3H8), nitrogen (N2)) and breakthrough experiments indicate that the MOF can separate CH4 efficiently from CH4/C2H6/C3H8 ternary mixture, with super high purity-CH4 production of 154.7 cm3 g-1. Additionally, the MOF shows higher CH4 capacity than N2, resulting in excellent separation performance for the CH4/N2 mixture. Notably, the binding sites of gases can be precisely determined by single-crystal X-ray data, further confirmed by molecular simulation. It is found that there are multiple hydrogen bonds and C─H···π interactions between the gases and the framework. This work offers an excellent candidate material for CH4 purification with both high capacity and separation efficiency.

A 2-fold interpenetrating 3D pillar-layered MOF for the gas separation and detection of metal ions

A 2-fold interpenetrating 3D pillar-layered MOF, which was assembled from a mixed-linker and paddle-wheel cluster, was successfully synthesized. It possesses good thermal and water stability as well as high selectivity for C2H6 over CH4 and CO2 over N2 under ambient conditions, which was further proved by breakthrough experiments. Moreover, this porous material exhibits good detection of Cu2+, [Co(NH3)6]3+ and Fe3+ in an aqueous solution.

Ultramicroporous Lonsdaleite Topology MOF with High Propane Uptake and Propane/Methane Selectivity for Propane Capture from Simulated Natural Gas

Propane (C3H8) is a widely used fuel gas. Metal-organic framework (MOF) physisorbents that are C3H8 selective offer the potential to significantly reduce the energy footprint for capturing C3H8 from natural gas, where C3H8 is typically present as a minor component. Here we report the C3H8 recovery performance of a previously unreported lonsdaleite, lon, topology MOF, a chiral metal-organic material, [Ni(S-IEDC)(bipy)(SCN)]n, CMOM-7. CMOM-7 was prepared from three low-cost precursors: Ni(SCN)2, S-indoline-2-carboxylic acid (S-IDECH), and 4,4'-bipyridine (bipy), and its structure was determined by single crystal X-ray crystallography. Pure gas adsorption isotherms revealed that CMOM-7 exhibited high C3H8 uptake (2.71 mmol g-1) at 0.05 bar, an indication of a higher affinity for C3H8 than both C2H6 and CH4. Dynamic column breakthrough experiments afforded high purity C3H8 capture from a gas mixture comprising C3H8/C2H6/CH4 (v/v/v = 5/10/85). Despite the dilute C3H8 stream, CMOM-7 registered a high dynamic uptake of C3H8 and a breakthrough time difference between C3H8 and C2H6 of 79.5 min g-1, superior to those of previous MOF physisorbents studied under the same flow rate. Analysis of crystallographic data and Grand Canonical Monte Carlo simulations provides insight into the two C3H8 binding sites in CMOM-7, both of which are driven by C-H···π and hydrogen bonding interactions.

Porous MOF Featuring 2D Intersecting Channels Based on a Pentanuclear Mn5(COO)10CO3 Cluster with Upgrading of Pipeline Natural Gas

Natural gas plays a crucial role in daily and industrial production, but the impurities contained in natural gas limit its further use. It is very important to develop adsorbents that can separate CH4 from multicomponent mixtures, but there are still many challenges and problems. Herein, a novel porous MOF {[Mn5(pbdia)2(CO3)(H2O)2] ↔ 5H2O ↔ 2DMF}n (pbdia = 2,2'-(5-carboxy-1,3-phenylene)bis(oxy) diterephthalic acid) was successfully synthesized based on a flexible pentacarboxylic acid ligand and a unique pentanuclear Mn5(COO)10CO3 cluster. The MOF reveals a 3D porous structure with 2D intersecting channels, which shows high C3H8, C2H6, and CO2 adsorption capacities and affinities over CH4. Moreover, the ideal adsorption solution theory selectivities of C3H8/CH4, C2H6/CH4, and CO2/CH4 can reach 263.0, 27.0, and 7.7, respectively, suggesting a potential for removing the low content of C3H8, C2H6, and CO2 from pipeline natural gas, which was further confirmed by breakthrough curves and GCMC simulations.

Halogen-modified metal-organic frameworks for efficient separation of alkane from natural gas

As a rich green energy source, natural gas is widely used in many fields such as the chemical industry, automobile energy, and daily life. However, it is very challenging to separate and recover C2H6 and C3H8 from natural gas. Metal-organic frameworks (MOFs) as an emerging type of multi-pore porous materials show huge potential in gas adsorption separation. Herein, we report pillar-layered MOFs, Ni (BDC)(DABCO)0.5 (DMOF-X), modified by halogen atoms (F, Cl, Br), and investigate their CH4/C2H6/C3H8 separation performance. The experimental results show that DMOF-Cl exhibited a extremely high adsorption capacity for C3H8 and C2H6. Under the conditions of 298 K and 100 kPa, the adsorption capacities for C3H8 and C2H6 on DMOF-Cl are as high as 6.23 and 4.94 mmol g-1, which are superior to the values for most of the porous materials that have been reported. In addition, DMOF-Cl also shows high C3H8/CH4 (5: 85, V/V) and C2H6/CH4 (10: 85, V/V) separation selectivities, with values of 130.9 and 12.5, respectively. Finally, DMOF-Cl also demonstrated great potential as an adsorbent for separating C3H8/C2H6/CH4.

Ligand-Functional Groups Induced Tuning MOFs' 2D into 1D Pore Channels for Pipeline Natural Gas Purification

The solvothermal reactions of CoCl₂  ⋅ 6H₂ O, 3,5-pyridinedicarboxylic acid (H₂ L) and isonicotinic acid (HL₁ )/3-amino isonicotinic acid (HL₂ )/3-chloro isonicotinic acid (HL₃ ) successfully led to three tfz-d topological pillar-layer [Co₄ (μ-F)₂ (COO)₆ (NC₅ H₄ )₄ ] cluster-based MOFs, namely, [Co₄ (μ-F)₂ (L)₂ (L₁ )₂  ⋅ 2DMA] ⋅ DMA ⋅ 2H₂ O (SNNU-Bai76, SNNU-Bai=Shaanxi Normal University Bai's group), [Co₄ (μ-F)₂ (L)₂ (L₂ )₂  ⋅ 2H₂ O] ⋅ 2DMA ⋅ 2H₂ O (SNNU-Bai77) and [Co₄ (μ-F)₂ (L)₂ (L₃ )₂  ⋅ 2H₂ O] ⋅ 2DMF ⋅ 2H₂ O (SNNU-Bai78). With the 2D pore channels in SNNU-Bai76 and SNNU-Bai77 being tuned to the 1D pore channel in SNNU-Bai78, C₃ H₈ and C₂ H₆ adsorption uptakes are apparently improved and the IAST selectivities of C₃ H₈ /CH₄ and C₂ H₆ /CH₄ almost remain, which indicate that SNNU-Bai78 may be one potential separation material for the pipeline natural gas purification. These were further confirmed by the breakthrough experiments for the simulated pipeline natural gas (C₃ H₈ /C₂ H₆ /CH₄  : 5/10/85 gas mixture) of three isostructural MOFs. Furthermore, GCMC simulations revealed that due to one of the pore channels blocked by Cl atoms in a couple of 3-chloro isonicotinic acid with the changed conformation as the pillar, the pore wall of the formed 1D pore channel in SNNU-Bai78 may interact with the adsorbed C₃ H₈ or C₂ H₆ molecule more strongly, for which more atoms of framework at the new adsorption site will interact with the adsorbed gas molecule by more intermolecular interactions. This was also evidenced by the increased binding energies, being consistent with the tuning of adsorption enthalpies for C₃ H₈ and C₂ H₆ gas molecules, and the reduced C₃ H₈ and C₂ H₆ gas diffusion coefficients in SNNU-Bai78. Very interestingly, this work is the first example of finely tuning the pore connectivity of MOFs toward strengthened host-guest interactions for the gas adsorption and separation.

A novel trigonal bipyramidal cage-based Zn(ii)-MOF featuring two types of trinuclear clusters with high gas sorption properties

A unique trigonal bipyramidal cage-based Zn(ii)-MOF built from a linear trinuclear pin-wheel cluster and a triangular trinuclear cluster was prepared and shows a moderate gas adsorption amounts and high selectivities towards C2Hn/CH4 and C2H2/CO2.

Synthesis, Structure and Highly Selective C3H8/CH4 and C2H6/CH4 Adsorptions of a (4,8)-c Ternary flu-Metal-organic Framework based upon both [Sc4O2(COO)8] and [Cu4OCl6] Clusters

A new ternary flu topological metal-organic framework based upon the torsional cubic 8-connected [Sc4O2(COO)8] cluster and the tetrahedral 4-connected [Cu4OCl6] cluster, namely, [Sc4O2(Cu4Cl6O)2(L)8•5H2O]•xGuest (SNNU-Bai69; SNNU-Bai = Shaanxi Normal University, Bai’s...

Bottom-up synthesis strategy of a two-dimensional {Fe5} cluster-based coordination polymer: stepwise formation of a {Fe5} cluster and its dimension augmentation

A 2D cluster-based coordination polymer of {Fe5}-2D was developed by hierarchical dimension augmentation from its 1D coordination polymer of {Fe5}-1D and discrete 0D cluster of {Fe5}-0D. And a possible bottom-up synthesis mechanism was proposed.