Flexible Microporous Framework for One-Step Acquisition of Ethylene from Ternary C2 Hydrocarbons.

One-step purification of ethylene (C2H4) from ternary C2 hydrocarbon mixtures is a crucial task and an enduring challenge because of their similar molecular size and physical properties. Owing to their intriguing structural dynamics, flexible MOFs have attracted more attention for gas adsorption and separation. Herein, we report a flexible MOF FJI-W-66 that exhibits rarely seen "breathing" behaviors for C2 hydrocarbons. Upon activation, the channels of guest-free FJI-W-66a significantly contract to a nearly closed-pore state. FJI-W-66a shows the stepwise adsorption isotherms for C2 hydrocarbons, which suggests the occurrence of structural transformation between less open and more open phases. Breakthrough experiments provide evidence that FJI-W-66a can selectively separate C2H4 from C2H2/C2H4/C2H6 mixtures with different ratios under ambient conditions, realizing the one-step acquisition of C2H4 from ternary C2 hydrocarbons.

An Ultra-stable Supramolecular Framework Based on Consecutive Side-by-side Hydrogen Bonds for One-step C2H4/C2H6 Separation.

The one-step efficient separation of high-purity C2H4 from C2H4/C2H6 mixtures by hydrogen-bonded organic frameworks (HOFs) faces two problems: lack of strategies for constructing stable pores in HOFs and how to obtain high C2H6 selectivity. Herein, we have developed a microporous Mortise-Tenon-type HOF (MTHOF-1, MT is short for Mortise-Tenon structure) with a new self-assembly mode for C2H4/C2H6 separation. Unlike previous HOFs which usually possess discrete head-to-head hydrogen bonds, MTHOF-1 is assembled by unique consecutive side-by-side hydrogen bonds, which result in mortise-and-tenon pores decorated with orderly arranged amide groups and benzene rings. As expected, MTHOF-1 exhibits excellent stability under various conditions and shows clear separation trends for C2H6/C2H4. The IAST selectivity is as high as 2.15 at 298 K. More importantly, dynamic breakthrough experiments have demonstrated that MTHOF-1 can effectively separate the C2H6/C2H4 feed gas to obtain polymer-grade C2H4 in one step even under high-humidity conditions.

Stable Fluorinated Hybrid Microporous Material for the Efficient Separation of C2-C3 Alkyne/Alkene Mixtures.

The separation of C2-C3 alkyne/alkene mixtures is important but difficult work thanks to their similar physical and chemical properties. Crystalline porous materials with high alkyne adsorption and prominent separation selectivity of alkyne/alkene mixtures have been extensively investigated because of their energy-saving merits. Herein, we report a fluorinated hybrid microporous material (FJI-W1) that exhibits unexpected water and thermal stability. Gas sorption isotherms show that FJI-W1 has ultrahigh C2H2 and C3H4 adsorption capacities of 150 and 159 cm3/g, respectively. Furthermore, dynamic breakthrough experiments indicate that the intervals of breakthrough time between the two gases for 1:99 (v/v) C2H2/C2H4 and 1:99 (v/v) C3H4/C3H6 can be up to 230 and 600 min/g, respectively. Additionally, the tests with different flow rates and three-cycle breakthrough tests demonstrate that FJI-W1 has a remarkable C2-C3 alkyne/alkene separation performance.

A Metal-Organic Framework with Nonpolar Pore Surfaces for the One-Step Acquisition of C2 H4 from a C2 H4 and C2 H6 Mixture.

Because C2 H4 plays an essential role in the chemical industry, economical and energy-efficient separation of ethylene (C2 H4 ) from ethane (C2 H6 ) is extremely important. With the exception of energy-intensive cryogenic distillation, there are few one-step methods to obtain polymer-grade (≥99.95 % pure) C2 H4 from C2 H4 /C2 H6 mixtures. Here we report a highly stable metal-organic-framework (MOF) FJI-H11-Me(des) (FJI-H=Hong's group in Fujian Institute of Research on the Structure of Matter) which features one-dimensional hexagonal nonpolar pore surfaces constructed by aromatic rings and alkyl groups. This FJI-H11-Me(des) adsorbs C2 H6 rather than C2 H4 between 273 and 303 K. Practical breakthrough experiments with C2 H4 containing 1 % C2 H6 have shown that FJI-H11-Me(des) can realize the acquisition in one-step of polymer-grade, 99.95 % pure C2 H4 under various conditions including different gas flow rates, temperatures and relative humidity.

The Compatibility of COFs Cathode and Optimized Electrolyte for Ultra-Long Lifetime Rechargeable Aqueous Zinc-Ion Battery.

Rechargeable aqueous zinc-ion batteries (RAZIBs) are attractive due to their affordability, safety, and eco-friendliness. However, their potential is limited by the lack of high-capacity cathodes and compatible electrolytes needed for reliable performance. Herein, we have presented a compatibility strategy for the development of a durable and long-lasting RAZIBs. The covalent organic frameworks (COFs) based on anthraquinone (DAAQ-COF) is created and utilized as the cathode, with zinc metal serving as the anode. The electrolyte is made up of an aqueous solution containing zinc salts at various concentrations. The COF cathode has been designed to be endowed with a rich array of redox-active groups, enhancing its electrochemical properties. Meanwhile, the electrolyte is formulated using triflate anions, which have exhibited superiority over sulfate anions. This strategy lead to the development of an optimized COF cathode with fast charging capability, high Coulombic efficiency (nearly 100 %) and long-term cyclability (retention rate of nearly 100 % at 1 A g-1 after 10000 cycles). Moreover, through experimental analysis, a co-insertion mechanism involving Zn2+ and H+ in this cathode is discovered for the first time. These findings represent a promising path for the advancement of organic cathode materials in high-performance and sustainable RAZIBs.

Water-Stable Microporous Bipyrazole-Based Framework for Efficient Separation of MTO Products.

Recently, methanol-to-olefins (MTO) technology has been widely used. The development of new adsorbents to separate MTO products and obtain high-purity ethylene (C2H4) and propylene (C3H6) has become an urgent task. Herein, an exceptionally highly water-stable metal-organic framework (MOF), [Cu3(OH)2(Me2BPZ)2]·(solvent)x (1) (H2Me2BPZ = 3,3'-dimethyl-1H,1'H-4,4'-bipyrazole) with hexagonal pores, has been elaborately designed and constructed. After being soaked in water for 7 days, it still maintains its structure, and the uptake of N2 at 77 K is unchanged. The adsorption capacity of C3H6 can reach 138 cm3 g-1, while the uptake of C2H4 is only 52 cm3 g-1 at 298 K and 1 bar. The dynamic breakthrough experiments show that the mixture of C3H6/C2H4 (50/50, v/v) can be efficiently separated in one step. High-purity C2H4 and C3H6 can be obtained through an adsorption and desorption cycle and the yields of C2H4 (purity ≥ 99.95%) and C3H6 (purity ≥ 99%) are 84 and 48 L kg-1, respectively. Surprisingly, when the flow rate is increased, the separation performance has no obvious change. Additionally, humidity has no effect on the separation performance. Finally, theoretical simulations indicate that there are stronger interactions between the C3H6 molecule and the framework, which are beneficial to capturing C3H6 over C2H4.

A proton-conductive metal-organic framework based on imidazole and sulphate ligands.

A metal-organic framework (MOF) built from a combination of metal cations, neutral azole ligands and sulphate anions, [Cu2(DHBDI)3(SO4)2]n (1, DHBDI = 1H,5H-benzo[1,2-d:4,5-d']diimidazole), was synthesized. MOF 1 exhibits good chemical stability in acids, bases and boiling water while showing high hydrophilicity. Meanwhile, MOF 1 exhibits a proton conductivity of 1.14 × 10-3 S cm-1 at 90 °C and 98% RH, among the best for MOF materials with uncoordinated N sites. Temperature-dependent conductivity measurements suggest a vehicle mechanism (Ea = 0.64 eV) for proton transport.

Rational Pore Design of a Cage-like Metal-Organic Framework for Efficient C2H2/CO2 Separation.

Considering the importance of C2H2 in industry, it is of great significance to develop porous materials for efficient C2H2/CO2 separation. Besides the high selectivity, the C2H2 adsorption capacity is another vital factor in C2H2/CO2 separation. However, the "trade-off" between these two factors is still perplexing. Rational pore design of metal-organic frameworks (MOFs) has been proven to be an effective way to solve the above problem. In this work, we have appropriately combined three kinds of strategies in the design of the MOF (FJI-H33), i.e., the introduction of open metal sites, construction of cage-like cavities, and adjustment of moderate pore size. As anticipated, FJI-H33 exhibits both outstanding C2H2 adsorption capacity and high C2H2/CO2 selectivity. At 298 K and 100 kPa, the C2H2 storage capacity of FJI-H33 is 154 cm3/g, while the CO2 uptake is only 80 cm3/g. The ideal adsorbed solution theory (IAST) selectivity of C2H2/CO2 (50:50) is calculated as high as 15.5 at 298 K. More importantly, the excellent practical separation performance was verified by breakthrough experiments. In addition, the calculation of adsorption sites and relevant energy by density functional theory (DFT) provides a good explanation for the excellent separation performance and pore design strategy.

Heterometallic Dual-Liganded AE-Ln-CPs Luminescent Probes for Efficient Sensing of Fe(III) Ions.

Iron ion is widely present in the environment and in biological systems, and are indispensable trace elements in living organisms, so development of an efficient and simple sensor for sensing Fe(III) ions has attracted much attention. Here, six heterometallic AE-Ln coordination polymers (CPs) [Ln2 (pda)4(Hnda)2Ca2(H2O)2]·MeOH (Ln = Eu (1), Tb (2); H2pda = 2,6-pyridinedicarboxylic acid, H2nda = 2,3-naphthalenedicarboxylic acid), [Ln (pda)2 (nda)AE2(HCOO)(H2O)] (AE = Sr, Ln = Eu (3), Tb (4); AE = Ba, Ln = Eu (5), Tb (6)) with two-dimensional (2D) layer structures were synthesized by hydrothermal method. All of them were characterized by elemental analysis, XRD, IR, TG, as well as single crystal X-ray diffraction. They all show infinite 2D network structure, where complexes 1 and 2 are triclinic with space group of P 1 ¯ , while 3-6 belong to the monoclinic system, space group P21/n . The solid-state fluorescence lifetimes of complexes 1, 3 and 5 are τobs1 = 1930.94, 2049.48 and 2,413.04 µs, respectively, and the quantum yields Ф total are 63.01, 60.61, 87.39%, respectively, which are higher than those of complexes 2, 4 and 6. Complexes 1-6 all exhibited efficient fluorescence quenching response to Fe3+ ions in water, and were not interfered by the following metal ions: Cu2+, Cd2+, Mg2+, Ni2+, Co2+, Ca2+, Ba2+, Sr2+, Li+, Na+, K+, Al3+, Fe2+, Pb2+, Cr3+, Mn2+ and Zn2+. The quenching coefficient K SV for complexes 1-6 is 1.41 × 105 M-1, 7.10 × 104 M-1, 1.70 × 105 M-1, 1.57 × 105 M-1, 9.37 × 104 M-1, 1.27 × 105 M-1, respectively. The fluorescence quenching mechanism of these complexes towards Fe3+ ions was also investigated. It is possible that the weak interaction formed between the complexes and the Fe3+ ions reduce the energy transfer from the ligand to the Ln3+ ion, producing the emission burst effect. This suggests that complexes 1-6 can be candidate for efficient luminescent sensor of Fe3+.