Bioinspired Design of a Giant [Mn86 ] Nanocage-Based Metal-Organic Framework with Specific CO2 Binding Pockets for Highly Selective CO2 Separation.

Adsorption-based removal of carbon dioxide (CO2 ) from gas mixtures has demonstrated great potential for solving energy security and environmental sustainability challenges. However, due to similar physicochemical properties between CO2 and other gases as well as the co-adsorption behavior, the selectivity of CO2 is severely limited in currently reported CO2 -selective sorbents. To address the challenge, we create a bioinspired design strategy and report a robust, microporous metal-organic framework (MOF) with unprecedented [Mn86 ] nanocages. Attributed to the existence of unique enzyme-like confined pockets, strong coordination interactions and dipole-dipole interactions are generated for CO2 molecules, resulting in only CO2 molecules fitting in the pocket while other gas molecules are prohibited. Thus, this MOF can selectively remove CO2 from various gas mixtures and show record-high selectivities of CO2 /CH4 and CO2 /N2 mixtures. Highly efficient CO2 /C2 H2 , CO2 /CH4 , and CO2 /N2 separations are achieved, as verified by experimental breakthrough tests. This work paves a new avenue for the fabrication of adsorbents with high CO2 selectivity and provides important guidance for designing highly effective adsorbents for gas separation.

Theoretical and experimental insights into the mechanisms of C6/C6 PFPiA degradation by dielectric barrier discharge plasma.

As an emerging alternative legacy perfluoroalkyl substance, C6/C6 PFPiA (perfluoroalkyl phosphinic acids) has been detected in aquatic environments and causes potential risks to human health. The degradation mechanisms of C6/C6 PFPiA in a dielectric barrier discharge (DBD) plasma system were explored using validated experimental data and density functional theory (DFT) calculations. Approximately 94.5% of C6/C6 PFPiA was degraded by plasma treatment within 15 min at 18 kV. A relatively higher discharge voltage and alkaline conditions favored its degradation. C6/C6 PFPiA degradation was attributed to attacks of •OH, •O2-, and 1O2. Besides PFHxPA and C2 -C6 shorter-chain perfluorocarboxylic acids, several other major intermediates including C4/C6 PFPiA, C4/C4 PFPiA, and C3/C3 PFPiA were identified. According to DFT calculations, the potential energy surface was proposed for possible reactions during C6/C6 PFPiA degradation in the discharge plasma system. Integrating the identified intermediates and DFT results, C6/C6 PFPiA degradation was deduced to occur by stepwise losing CF2, free radical polymerization, and C-C bond cleavage. Furthermore, the DBD plasma treatment process decreased the toxicity of C6/C6 PFPiA to some extent. This study provides a comprehensive understanding of C6/C6 PFPiA degradation by plasma advanced oxidation.

An uncommon multicentered ZnI-ZnI bond-based MOF for CO2 fixation with aziridines/epoxides.

A novel cluster-based MOF with uncommon multicentered ZnI-ZnI bonds {[K1.2Na2.8ZnI8(HL)12]·4H2O}n (HL = tetrazole monoanion) (1) was synthesized, which showed higher stability than the reported ZnI-ZnI bonded compounds. Moreover, 1 can effectively and circularly catalyze the cyclization of CO2 and aziridines or epoxides with five substituent groups. Importantly, this is the first time that the catalytic properties of MOFs with multicentered metal-metal bonded clusters as the catalyst have been studied.

Photocatalytic Hydrogen Evolution Based on Cobalt-Organic Framework with High Water Vapor Adsorption.

Photocatalytic hydrogen evolution is desired to effectively alleviate the serious crisis of energy and the environment, and the utilization of low-cost photocatalysts, especially cobalt-based MOF catalysts, is meaningful, but rarely investigated. Herein, through a self-assembly strategy, we synthesized a Co clusters-based MOF (Co3-XL) by the ligand N,N'-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxdiimide bi(1,2,4-triazole), containing abundant carbonyl O atoms in the channels of the 3D skeleton, and a large porosity of 50.7%. The as-synthesized MOF can be stable in the pH range of 3-10 and shows a narrow band gap of 1.82 eV. Furthermore, its maximum amount of water absorption can reach 192 cm3/g. Under irradiation of simulated solar light, the rate of hydrogen evolution is 23.05 µmol·h-1·g-1 among 12 h with the presence of co-catalyst Pt and photosensitizer RhB. The reaction mechanism has been probed by the transient photocurrent response and steady-state photoluminescence spectra. Therefore, as a narrow band gap photocatalyst, the cobalt clusters-based MOF (Co3-XL) has potential applications for hydrogen evolution from water.

Decomposition of highly persistent perfluorooctanoic acid by hollow Bi/BiOI1-xFx: Synergistic effects of surface plasmon resonance and modified band structures.

Perfluorooctanoic acid (PFOA) is highly stable due to the strong CF bond and extremely difficult to be removed by conventional photocatalysts. In this study, Bi doped BiOI1-xFx solid solutions with hollow microsphere structure were prepared through a facile one-step hydrothermal method. Compared with pure BiOI and BiOF, the band gap of the Bi/BiOI1-xFx solid solutions was significantly reduced, thus promoting the visible light absorbance. The cavity structure of the BiOI1-xFx solid solutions enhanced the surface areas and active sites for reaction. The local electromagnetic field dominated by surface plasmon resonance (SPR) effect of Bi metal on the surface favored the separation of the photoinduced charge pairs. As a consequence, Bi/BiOI0.8F0.2 (x = 0.20, the doping amount of fluorine was 20 %) composite displayed the best photocatalytic performance for decomposing PFOA, and 40 mg/L PFOA could be removed within 2 h illumination. The degradation rate constant (k = 0.0375 min-1) of PFOA by Bi/BiOI0.8F0.2 was about tenfold of that by pure BiOI and BiOF. Superoxide radical (·O2-) predominated in the degradation of PFOA by Bi/BiOI0.8F0.2, and the possible degradation pathway of PFOA by Bi/BiOI0.8F0.2 was proposed. This work provides a highly efficient catalyst for the practical application in removal of highly persistent PFOA.

Highly Efficient Conversion of Propargylic Amines and CO2 Catalyzed by Noble-Metal-Free [Zn116 ] Nanocages.

The reaction of propargylic amines and CO2 can provide high-value-added chemical products. However, most of catalysts in such reactions employ noble metals to obtain high yield, and it is important to seek eco-friendly noble-metal-free MOFs catalysts. Here, a giant and lantern-like [Zn116 ] nanocage in zinc-tetrazole 3D framework [Zn22 (Trz)8 (OH)12 (H2 O)9 ⋅8 H2 O]n Trz=(C4 N12 O)4- (1) was obtained and structurally characterized. It consists of six [Zn14 O21 ] clusters and eight [Zn4 O4 ] clusters. To our knowledge, this is the highest-nuclearity nanocages constructed by Zn-clusters as building blocks to date. Importantly, catalytic investigations reveal that 1 can efficiently catalyze the cycloaddition of propargylic amines with CO2 , exclusively affording various 2-oxazolidinones under mild conditions. It is the first eco-friendly noble-metal-free MOFs catalyst for the cyclization of propargylic amines with CO2 . DFT calculations uncover that ZnII ions can efficiently activate both C≡C bonds of propargylic amines and CO2 by coordination interaction. NMR and FTIR spectroscopy further prove that Zn-clusters play an important role in activating C≡C bonds of propargylic amines. Furthermore, the electronic properties of related reactants, intermediates and products can help to understand the basic reaction mechanism and crucial role of catalyst 1.

High Uptake of ReO4 - and CO2 Conversion by a Radiation-Resistant Thorium-Nickle [Th48 Ni6 ] Nanocage-Based Metal-Organic Framework.

Assembled from [Th48 Ni6 ] nanocages, the first transition-metal (TM)-thorium metal-organic framework (MOF, 1) has been synthesized and structurally characterized. 1 exhibits high solvent and acid/base stability, and resistance to 400 kGy ß irradiation. Notably, 1 captures ReO4 - (an analogue of radioactive 99 TcO4 - , a key species in nuclear wastes) with a maximum capacity of 807 mg g-1 , falling among the largest values known to date. Furthermore, 1 can enrich methylene blue (MB) and can also serve as an effective and recyclable catalyst for CO2 fixation with epoxides; there is no significant loss of catalytic activity after 10 cycles. Theoretical studies with nucleus-independent chemical shifts and natural bond orbital analysis reveal that the [Th6 O8 ] clusters in 1 have a unique stable electronic structure with (d-p)π aromaticity, partially rationalising 1's stability.

A Cuprous/Lanthanide-Organic Framework as the Luminescent Sensor of Hypochlorite.

A new 3D framework {[Eu2 Cu(IN)5 (CO3 )(H2 O)] ⋅3 H2 O}n  (1) was obtained and structurally characterized, containing CuI and an unusual lanthanide duplex chain. The luminescent explorations of compound 1 suggest that 1 could emit the characteristic emission of CuI , and 1 can act as the luminescent sensor of ClO- with the detection limit of 10-5  m. Notably, 1 represents the first example of MOF-based sensor for detecting ClO- .

A multifunctional MOF as a recyclable catalyst for the fixation of CO2 with aziridines or epoxides and as a luminescent probe of Cr(vi).

A multifunctional metal-organic framework (1) containing 24-nuclear zinc nanocages shows high solvent- and pH-stability. Compound 1 can be employed as a catalyst for the conversion of CO2 with aziridines or epoxides, which can be reused at least ten times just by a simple and rapid method. The PXRD of compound 1 after ten recyclings remains well consistent with the original one. The inductively coupled plasma measurement of a reaction filtrate revealed that only trace amount leakage of Zn2+ was observed, indicating that the framework did not collapse after recyclings. Compound 1 can effectively catalyze the cycloaddition reaction of CO2 and five aziridines or five epoxides with different substituent groups. To our knowledge, this is the first multifunctional MOF-based catalyst used for the conversion of CO2 with aziridines or epoxides. Furthermore, luminescence investigations reveal that compound 1 can also act as a luminescent probe for chromium(vi) anion species, which is seriously harmful to humans and the environment. After five cycle tests, the PXRD of compound 1 is still in accordance with the original one, indicating that compound 1 can serve as a circulatory luminescent probe for Cr(vi) anions.

Several [Gd-M] Heterometal-Organic Frameworks with [Gdn] as Nodes: Tunable Structures and Magnetocaloric Effect.

Tunable structures and magnetocaloric effect (MCE) of seven MOFs with [Gdn] as nodes are explored. The [Gdn] node is realized from mononuclear [Gd] to binuclear paddle-wheel [Gd2], tetranuclear tetrahedral [Gd4], and pentanuclear trigonal bipyramidal [Gd5]. Meanwhile, the magnetic entropy changes from 19.4 to 46.0 J·kg-1·K-1. The results reveal that the effect of magnetic density on MCE plays a dominant role for Gd3+-based compounds, and high spin ground state of Mn2+ (S = 5/2) is more favorable to achieve high MCE than that with Zn2+, Co2+, and Ni2+ (Co2+, S = 3/2; Ni2+, S = 1). To our knowledge, it is the first report that MCE is controlled by various clusters as nodes in MOFs.

A Porous Metal-Organic Framework Assembled by [Cu30] Nanocages: Serving as Recyclable Catalysts for CO2 Fixation with Aziridines.

Based on a novel ligand 5-(2,6-bis(4-carboxyphenyl)pyridin-4-yl)isophthalic acid (H4BCP) with large skeletons, a unique porous framework {[Cu2(BCP)(H2O)2]·3DMF} n (1) assembled by nano-sized and censer-like [Cu30] cages is successfully obtained and structurally characterized. In 1, the large 1D channel in frameworks and window size in the nanocages can enrich methylene blue and capture CO2, exhibiting the promising applications in environmental protection. More importantly, the explorations on the cycloaddition reaction of CO2 and aziridines with various substituents suggest that 1 can serve as an efficient heterogeneous catalyst for CO2 conversion with aziridines in a solvent-free system, which can be reused at least ten times without any obvious loss in catalytic activity. This is the first example of metal-organic framework (MOF)-based catalysts in converting CO2 into high-value oxazolidinones through activating aziridines and CO2, further extending the applications of MOFs materials in catalysis.

A Bifunctional Europium-Organic Framework with Chemical Fixation of CO2 and Luminescent Detection of Al3.

A novel three-dimensional lanthanide-organic framework {[Eu(BTB)(phen)]·4.5DMF·2H2O}n (1) has been synthesized. Structural characterization suggests that framework 1 possesses one-dimensional channels with potential pore volume, and the large channels in the framework can capture CO2. Interestingly, investigations on the cycloaddition reaction of CO2 and epoxides reveal that compound 1 can be considered as an efficient catalyst for CO2 fixation with epoxides under 1 atm pressure. Importantly, 1 can be reused at least five times without any obvious loss in catalytic activity. Furthermore, the luminescent explorations of 1 reveal that 1 can act as a recyclable sensor of Al3+, and the corresponding detection limit can reach 5 × 10-8 M (1.35 ppb), which is obviously lower than the United States Environmental Protection Agency's recommended level of Al3+ in drinking water (200 ppb). These results show that 1 has a level of sensitivity higher than that of other reported MOF-based sensors of Al3+.

Lanthanide-based metal-organic frameworks as luminescent probes.

Lanthanide-based metal-organic frameworks (Ln-MOFs), as notable materials, are constructed by Ln3+ ions and organic ligands, or Ln3+ ions functionalizing non-Ln-MOFs, and exhibit promising applications in various fields. Over the past decades, quite a lot of investigations of Ln-MOFs have been carried out, and many good results have been obtained. Among these results, Ln-MOFs as luminescent probes for unique detection are gradually becoming a hot topic due to their fast and effective luminescent response for the targeted substance. In this perspective article, we discuss the construction of luminescent Ln-MOFs, their applications in possible detection mechanisms, and summarize some examples of Ln-MOFs as luminescent probes for sensing cations, anions and small molecules.

Unique (3,4,10)-Connected Lanthanide-Organic Framework as a Recyclable Chemical Sensor for Detecting Al(3.).

Three isostructural Ln-BTB frameworks (Ln = Eu (1), Dy (2), Yb (3)) were synthesized and structurally characterized, in which mononuclear and trinuclear [Ln3] units as nodes construct unprecedented (3,4,10)-connected 3D frameworks with (4·6·8)4(4·8(2))2(4·8(5))(6(2)·8(4))(4(5)·6(8)·8(26)·10(6)) point symbol. The luminescent investigations revealed that compound 1 can sensitively and selectively detect Al(3+), but comparably compound 2 could not detect Al(3+) among various cations. More importantly, 1 as an Al(3+) sensor can be reused at least five times, which represents the first recyclable metal organic framework (MOF)-supported Al(3+) sensor. Additionally, magnetic investigations on 2 also were carried out, showing a single-molecule-magnet behavior.

First tetrazole-bridged d-f heterometallic MOFs with a large magnetic entropy change.

A novel 3D tetrazole-bridged 3d-4f heterometallic MOF {(H3O)3[Gd3Mn2(Trz)4]·12H2O}n (1) with a hexanuclear [Gd6] cluster was obtained via in situ [2+3] cycloaddition reaction and structurally characterized, possessing good solvent and thermal stabilities, as well as a large magnetic entropy change -ΔS(m) = 40.3 J kg(-1) K(-1) for ΔH = 7 T at 2.0 K. To our knowledge, it is the first example of tetrazole-bridged 3d-4f heterometallic MOFs.

A water-stable lanthanide-organic framework as a recyclable luminescent probe for detecting pollutant phosphorus anions.

A novel 3D Eu-BTB framework () containing three types of 1D channels was synthesized and structurally characterized. Compound exhibits high thermostability and water stability with the pH range from 2 to 12. Additionally, the luminescence explorations revealed that can sensitively and selectively detect pollutant PO4(3-) among various colourless anions. More importantly, represents the first example of regenerable MOF-based luminescent probes for detecting PO4(3-).

Lanthanide organic framework as a regenerable luminescent probe for Fe(3+).

A unique three-dimensional Tb-BTB framework (1) with two types of one-dimensional channels was obtained and structurally characterized, exhibiting high thermal stability. Luminescent investigations reveal that 1 can detect Fe(3+) with relatively high sensitivity and selectivity. Importantly, 1 as the luminescent probe of Fe(3+) can be simply and quickly regenerated, which represents a rare example in reported luminescent sensors of Fe(3+).