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Adsorptive separation by porous solids provides an energy-efficient alternative for the purification of important chemical species compared to energy-intensive distillations. Particularly, the separation of linear hexane isomers from its branched counterparts is crucial to produce premium grade gasoline with high research octane number (RON). Herein, we report the synthesis of a new, flexible zinc-based metal-organic framework, [Zn5(μ3-OH)2(adtb)2(H2O)5·5 DMA] (Zn-adtb), constructed from a butterfly shaped carboxylate linker with underlying (4,8)-connected scu topology capable of separating the C6 isomers nHEX, 3MP, and 23DMB. The sorbate-sorbent interactions and separation mechanisms were investigated and analyzed through in situ FTIR, solid state NMR measurements and computational modeling. These studies reveal that Zn-adtb discriminates the nHEX/3MP isomer pair through a kinetic separation mechanism and the nHEX/23DMB isomer pair through a molecular sieving mechanism. Column breakthrough measurements further demonstrate the efficient separation of linear nHEX from the mono- and dibranched isomers.

Fluorosis has been regarded as a worldwide disease that seriously diminishes the quality of life through skeletal embrittlement and hepatic damage. Effective detection and removal of fluorinated chemical species such as fluoride ions (F-) and perfluorooctanoic acid (PFOA) from drinking water are of great importance for the sake of human health. Aiming to develop water-stable, highly selective and sensitive fluorine sensors, we have designed a new luminescent MOF In(tcpp) using a chromophore ligand 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine (H4tcpp). In(tcpp) exhibits high sensitivity and selectivity for turn-on detection of F- and turn-off detection of PFOA with a detection limit of 1.3 μg L-1 and 19 μg L-1, respectively. In(tcpp) also shows high recyclability and can be reused multiple times for F- detection. The mechanisms of interaction between In(tcpp) and the analytes are investigated by several experiments and DFT calculations. These studies reveal insightful information concerning the nature of F- and PFOA binding within the MOF structure. In addition, In(tcpp) also acts as an efficient adsorbent for the removal of F- (36.7 mg g-1) and PFOA (980.0 mg g-1). It is the first material that is not only capable of switchable sensing of F- and PFOA but also competent for removing the pollutants via different functional groups.

Inorganic semiconductor materials are best known for their superior physical properties, as well as their structural rigidity and stability. However, the poor solubility and solution-processability of these covalently bonded network structures has long been a serious drawback that limits their use in many important applications. Here, we present a unique and general approach to synthesize robust, solution-processable, and highly luminescent hybrid materials built on periodic and infinite inorganic modules. Structure analysis confirms that all compounds are composed of one-dimensional anionic chains of copper iodide (CumIm+22-) coordinated to cationic organic ligands via Cu-N bonds. The choice of ligands plays an important role in the coordination mode (μ1-MC or μ2-DC) and Cu-N bond strength. Greatly suppressed nonradiative decay is achieved for the μ2-DC structures. Record high quantum yields of 85% (λex = 360 nm) and 76% (λex = 450 nm) are obtained for an orange-emitting 1D-Cu4I6(L6). Temperature dependent PL measurements suggest that both phosphorescence and thermally activated delayed fluorescence contribute to the emission of these 1D-AIO compounds, and that the extent of nonradiative decay of the μ2-DC structures is much less than that of the μ1-DC structures. More significantly, all compounds are remarkably soluble in polar aprotic solvents, distinctly different from previously reported CuI based hybrid materials made of charge-neutral CumXm (X = Cl, Br, I), which are totally insoluble in all common solvents. The greatly enhanced solubility is a result of incorporation of ionic bonds into extended covalent/coordinate network structures, making it possible to fabricate large scale thin films by solution processes.

One of the primary concerns in the development of new chemical reactions pertains to the choice of solvents, many of which can have harmful ecological impacts. Additionally, a major portion of waste generated in the chemical and pharmaceutical industries comes from the solvents employed. The elimination of solvent usage is highly desirable for creation of environmentally friendly chemical processes as it leads to a substantial reduction in waste production. Accordingly, a novel neat reaction was developed for the synthesis of (β‐amino)nitriles as a prominent moiety through a domino process. It involved the use of silylphenyl triflates, Schiff bases, and acetonitrile (CH3CN) in a 1 : 1 : 1 ratio, among which CH3CN served as a starting material rather than a solvent. This reaction was initiated by caesium fluoride (CsF) to form an aryne through 1,2‐elimination followed by sequential 1,2‐addition, proton transfer, and a second 1,2‐addition. Complete conversion was carried out at 25 °C for 1.0 h to give (β‐amino)nitriles in 76–88 % yields. This solvent‐free reaction minimized waste production and reduced costs associated with extra reagents, solvents, and labour. It possesses a compelling E factor and impressive volume productivity. This reaction sets a new benchmark for solvent‐free aryne domino processes in green chemistry advancements. [ABSTRACT FROM AUTHOR]

As an alternative technology to energy intensive distillations, adsorptive separation by porous solids offers lower energy cost and higher efficiency. Herein we report a topology-directed design and synthesis of a series of Zr-based metal-organic frameworks with optimized pore structure for efficient separation of C6 alkane isomers, a critical step in the petroleum refining process to produce gasoline with high octane rating. Zr6O4(OH)4(bptc)3 adsorbs a large amount of n-hexane but excluding branched isomers. The n-hexane uptake is ~70% higher than that of a benchmark adsorbent, zeolite-5A. A derivative structure, Zr6O4(OH)8(H2O)4(abtc)2, is capable of discriminating all three C6 isomers and yielding a high separation factor for 3-methylpentane over 2,3-dimethylbutane. This property is critical for producing gasoline with further improved quality. Multicomponent breakthrough experiments provide a quantitative measure of the capability of these materials for separation of C6 alkane isomers. A detailed structural analysis reveals the unique topology, connectivity and relationship of these compounds.

Molecular exchange is a common step occurring in many technological processes such as competitive adsorption, chemical separation, capture, delivery, and release. However, the underlying principle is not fully understood, especially in nanoconfined environments where the energetics and kinetics of such processes can deviate from that on flat surfaces. In this paper, we unravel the mechanism of a molecular exchange process by studying the displacement of NO by H2O in Ni-MOF-74 in real-time using in situ infrared spectroscopy combined with ab initio calculations. We show that weakly bound H2O gradually displaces strongly bound NO on the metal sites by first weakening the M–N bond through forming H-bond and then moving the NO away so that it eventually desorbs. Interestingly, we further find that additional water facilitates this exchange by significantly lowering the kinetic barrier associated with this process as well as the overall energy of the final state. Although our study focuses on Ni-MOF-74, we believe that our finding and explanation of unexpected exchange phenomena—where strongly adsorbed molecules are apparently easily displaced by much weaker bound H2O—is applicable to a much larger group of frameworks and will be helpful in designing and improving MOFs for real-world applications where humidity is often present. [ABSTRACT FROM AUTHOR]

Simultaneous removal of C2H6 and C2H2 from C2H4 streams is of great importance in the petrochemical industry but remains a challenging task. To address this challenge, we have selected three isoreticular MOFs with high stability, low cost, and desirable scale-up ability, namely, MOF-303, MIL-160, and CAU-23 and assessed their potential in simultaneous removal of acetylene and ethane for ethylene purification. Each MOF exhibits desirable C2H2 and C2H6 uptake capacity (>5.5 mmol g−1 and >4 mmol g−1, respectively), as well as good C2H2/C2H4 selectivity (>2) and C2H6/C2H4 selectivity (>1.5). Notably, MOF-303 takes up 4.96 mmol g−1 C2H6 at 298 K and 1 bar, the highest value among the three MOFs, with C2H6/C2H4 selectivity in the range of 1.55–2.47. MIL-160 possesses a very high C2H2 uptake (9.1 mmol g−1) and C2H2/C2H4 selectivity, 10.6 (1 : 1, v/v), at 298 K, much higher than those of all other MOFs tested to date for simultaneous removal of C2H6 and C2H2 from C2H4. The results from breakthrough experiments confirm that all three MOFs demonstrate excellent performance for C2H4 purification in a ternary mixture of C2H6/C2H4/C2H2 (1 : 1 : 1, v/v/v). For MOF-303, MIL-160, and CAU-23, polymer-grade C2H4 up to 0.164, 0.21, and 0.181 mmol g−1 can be obtained from the equimolar ternary mixture in a single separation step from the breakthrough experiment. Additionally, DFT calculations have been performed to further investigate the mechanism of adsorption/separation for C2H6, C2H4, and C2H2. [ABSTRACT FROM AUTHOR]