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Adsorptive separation based on porous solid adsorbents has emerged as an excellent effective alternative to energy-intensive conventional separation methods in a low energy cost and high working capacity manner. However, there are few stable mesoporous metal–organic frameworks (MOFs) for efficient purification of methane from other light hydrocarbons in natural gas. Herein, we report a series of stable mesoporous MOFs, MIL-101-Cr/Fe/Fe-NH2, for efficient separation of CH4 and C3H8 from a ternary mixture CH4/C2H6/C3H8. Experimental results show that all three MOFs possess excellent thermal, acid/basic, and hydrothermal stability. Single-component adsorption suggested that they have high C3H8 adsorption capacity and commendable selectivity for C3H8 and C2H6 over CH4. Transient breakthrough experiments further certified the ability of direct separation of CH4 from simulated natural gas and indirect recovery of C3H8 from the packing column. Theoretical calculations illustrated that the van der Waals force proportional to the molecular weight is the key factor and that the structural integrity and defect can impact separation performances.

Due to the ultralow amounts of C 3 H 8 and C 2 H 6 gases, to design and synthesize water-stable MOFs that are promising for real-world efficient pipeline natural gas (NG) upgrading by the recovery of individual C 3 H 8 and C 2 H 6 gases is still a great challenge. Here, a N/O/F heteroatom-rich and rooflike [Cu(II) 4 Cu(I) 2 (COO) 4 (tetrazolyl) 6 ] cluster-based ultra-microporous tsi-MOF (SNNU-Bai68) was afforded as a multiple heteroatom-rich and curved-surface-shaped cluster-based ultramicroporous MOF and the first porous MOF based upon such rooflike [Cu(II) x Cu(I) y (tetrazolyl) z ] (2x+y−z)+ cluster. In SNNU-Bai68, the rooflike cluster was further assembled into a 1D chain secondary building block (SBB), which led to a high density of accessible potential adsorptive sites. Very interestingly, it exhibited the most promising balance of high gas adsorption uptakes at 0.01, 0.03, and 0.05 bar, high C 3 H 8 /CH 4 , C 3 H 8 /C 2 H 6 , and C 2 H 6 /CH 4 adsorption selectivities, moderate adsorption enthalpies, and high water and chemical stability for pipeline natural gas upgrading by the recovery of individual C 3 H 8 and C 2 H 6 gases, which was further confirmed by the breakthrough experiments of the gas mixtures with/without 74% RH. Furthermore, the SC-XRD and GCMC studies revealed that the successful separation of C 3 H 8 , C 2 H 6 , and CH 4 gases in SNNU-Bai68 is due to different synergistic effects of H-bonds between the frameworks at three adsorptive sites around each rooflike cluster and those different gas molecules, which were initially described systematically by the number of H atoms from the gas molecules, the total number of H-bonds within the synergistic H-bonds, and the binding energy of the framework at an adsorption site toward the gas molecules. In addition, this work may provide a method for the construction of a multiple heteroatom-rich and curved-surface-shaped cluster-based ultra-microporous MOF as a novel approach to build MOFs with polar pore surfaces, suitable pore sizes, and unique pore shapes to maximize the synergistic H-bonds between the framework and guests. KEYWORDS: N/O/F-rich MOF, rooflike cluster, chemically stable, pipeline natural gas upgrading, C 3 H 8 and C 2 H 6 recovery

Global warming associated with CO 2 emission has led to frequent extreme weather events in recent years. Carbon capture using porous solid adsorbents is promising for addressing the greenhouse effect. Herein, we report a series of robust metal− organic cages (MOCs) featuring various functional groups, such as methyl and amine groups, for CO 2 /N 2 separation. Significantly, the amine-group-functionalized MOC-QW-3-NH 2 displays the best selective CO 2 adsorption performance, as confirmed by singlecomponent adsorption and transient breakthrough experiments. The distinct CO 2 adsorption mechanism has been well studied via theoretical calculations, confirming that the amine groups play a vital role for efficiently selective CO 2 adsorption resulting from hierarchical adsorbate−framework interaction.

Deep SO 2 removal and recovery as industrial feedstock are of importance in flue-gas desulfurization and natural-gas purification, yet developing low-cost and scalable physisorbents with high efficiency and recyclability remains a challenge. Herein, we develop a viable synthetic protocol to produce DUT-67 with a controllable MOF structure, excellent crystallinity, adjustable shape/size, milli-to-kilogram scale, and consecutive production by recycling the solvent/modulator. Furthermore, simple HCl post-treatment affords depurated DUT-67-HCl featuring ultrahigh purity, excellent chemical stability, fully reversible SO 2 uptake, high separation selectivity (SO 2 /CO 2 and SO 2 /N 2 ), greatly enhanced SO 2 capture capacity, and good reusability. The SO 2 binding mechanism has been elucidated by in situ X-ray diffraction/infrared spectroscopy and DFT/GCMC calculations. The single-step SO 2 separation from a real quaternary N 2 /CO 2 /O 2 /SO 2 flue gas containing trace SO 2 is implementable under dry and 50% humid conditions, thus recovering 96% purity. This work may pave the way for future SO 2 capture-and-recovery technology by pushing MOF syntheses toward economic cost, scale-up production, and improved physiochemical properties.