Yolk-Shell Au NPs@Carbon Porous Nanoreactors Derived from ZIF-8: A High-Efficiency Catalyst for Three-Component Coupling Reaction.

A yolk-shell Au NPs@carbon porous nanoreactor with an active gold (Au) core and a porous carbon shell has been fabricated and demonstrates excellent high activity and cyclic stability as a heterogeneous catalyst for the three-component coupling reaction of aldehyde, amine, and alkyne. Remarkably, the unique yolk-shell nanostructure can protect gold nanoparticles (Au NPs) from aggregation, allow for efficient mass transport, and benefit substrate enrichment, giving rise to enhanced activity, stability, and recyclability.

Solvent-Induced In(III)-MOFs with Controllable Interpenetration Degree Performing High-Efficiency Separation of CO2/N2 and CO2/CH4.

Herein, three In(III)-based metal-organic frameworks (In-MOFs) with different degrees of interpenetration (DOI), namely In-MOF-1, In-MOF-2, and In-MOF-3, constructed by In3+ and Y-shaped ligands 4,4',4″-s-triazine-2,4,6-triyltribenzoate (H3TATB), are successfully synthesized through the ionothermal/solvothermal method. Subsequently, three novel In-MOFs, including noninterpenetration polycatenation, 2-fold interpenetrated, and 4-fold interpenetrated structure, are employed as the platform for systematically investigating the separation efficiency of CO2/N2, CO2/CH4, and CO2/CH4/N2 mixture gas system. Among them, In-MOF-2 shows the highest CO2 uptake capacities at 298 K and simultaneously possesses the low adsorption enthalpy of CO2 (26.4 kJ/mol at low coverage), a feature desirable for low-energy-cost adsorbent regeneration. The CO2/N2 (v: v = 15/85) selectivity of In-MOF-2 reaches 37.6 (at 298 K and 1 bar), also revealing outstanding selective separation ability from flue gases and purifying natural gas, affording a unique robust separation material as it has moderate DOI and pore size. In-MOF-2 shows exceptional stability and feasibility to achieve reproducibility. Aperture adjustment makes In-MOF-2 a versatile platform for selectively capturing CO2 from flue gases or purifying natural gas.

Pore Space Partitioning MIL-88(Co): Developing Robust Adsorbents for CO2/CH4 Separation Featured with High CO2 Adsorption and Rapid Desorption.

Metal-organic frameworks (MOFs) have attracted significant attention as sorbents for gas separation and purification. Ideally, an industrially potential adsorbent should combine exceptional gas uptake, excellent stability, and a lower regeneration energy; however, it remains a great challenge. Here, by utilizing the pore space partition (PSP) strategy, we develop three isostructural MOF materials (Co-BDC-TPB, Co-DCBDC-TPB, and Co-DOBDC-TPB) based on pristine MIL-88(Co). The three pore-space-partitioned crystalline microporous MOFs have triangular bipyramid cages and segmented one-dimensional channels, and among them, Co-DOBDC-TPB exhibits the highest CO2 uptake capacity (4.35 mmol g-1) and good CO2/N2 (29.7) and CO2/CH4 (6.2) selectivity. The selectivity-capacity synergy endows it with excellent CO2/N2 and CO2/CH4 separation performance. Moreover, Co-DOBDC-TPB can complete desorption within 10 min. The satisfactory CO2 adsorption ability can be attributed to both microporous aperture arising from PSP and modification of the pore surface by the polar hydroxy group, which enhances the interaction between Co-DOBDC-TPB and CO2 molecules significantly. The exceptional regeneration property may be due to its lower CO2 isosteric heat of adsorption (23.6 kJ/mol). The developed pore-space-partitioned MIL-88(Co) material Co-DOBDC-TPB may have potential application to flue gas and natural gas purification.

Green Synthesis of MOF-801(Zr/Ce/Hf) for CO2/N2 and CO2/CH4 Separation.

The purification of natural gas and the removal of carbon dioxide from flue gases are crucial to economize precious resources and effectively relieve a series of environmental problems caused by global warming. Metal-organic framework (MOF) materials have demonstrated remarkable performance and benefits in the area of gas separation; however, obtaining materials with high gas capacity and selectivity simultaneously remains difficult. In addition, harsh synthesis conditions and solvent toxicity have been restricted in large-scale production and industrial application. Therefore, MOF-801(Zr/Ce/Hf) was created based on the green synthesis of the MOF-801 construction unit by altering the kinds of metal salts, and the impact of three metal nodes on the performance of gas adsorption and separation was demonstrated by contrasting the three MOFs. The results showed that MOF-801(Ce) has the best CO2 adsorption capacity (3.3 mmol/g at 298 K), which also was demonstrated with in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results, CO2/CH4 (ideal adsorbed solution theory (IAST) = 13.28 at 298 K, 1 bar, CO2/CH4 = 1:1, v/v), and the separation performance of CO2/N2 (IAST = 57.46 at 298 K, 1 bar, CO2/N2 = 1:1, v/v) among the group. Green synthesis of MOF-801(Zr/Ce/Hf) is an ideal candidate for flue gas separation and methane purification because of its high regeneration capacity and strong cyclic stability.

Polymelamine Formaldehyde-Coated MIL-101 as an Efficient Dual-Functional Core-Shell Composite to Catalyze the Deacetalization-Knoevenagel Tandem Reaction.

Porous organic polymer (POP) coated on a metal-organic framework (MOF) has the functions and advantages of MOF and POP at the same time and has excellent catalytic ability. In this study, an efficient dual-functional core-shell composite MOF@POP with Lewis acid and Brønsted base sites was synthesized using the impregnation method in which MIL-101(Cr) was the core component and polymelamine formaldehyde (PMF) was the shell component. Most importantly, the obtained MIL-101(Cr)@PMF showed perfect catalytic activity in the deacetalization-Knoevenagel tandem reaction. In addition, it could still maintain ultrahigh physical and chemical stability.

Trifunctional Metal-Organic Framework Catalyst for CO2 Conversion into Cyclic Carbonates.

Herein, we reported a facile strategy for the preparation of trifunctional ionic metal-organic frameworks (MOFs) incorporating imidazolium cation functionalities. This strategy exploits the Debus-Radziszewski reaction to create the cationic imidazole ring by postsynthetic modification, meanwhile introducing exchangeable counteranions. On the basis of this strategy, MIL-101-IMOH-Br- has been synthesized, which combines Lewis acidic sites, Brønsted acidic sites, and nucleophilic centers to achieve catalysis for the carbon dioxide-epoxide cycloaddition into cyclocarbonate without any cocatalyst and solvent.

Superhydrophobic/Superoleophilic MOF Composites for Oil-Water Separation.

A universal strategy is developed to construct metal-organic framework (MOF)-based superhydrophobic/superoleophilic materials by the reaction of activated MOFs and octadecylamine. In particular, S-MIL-101(Cr) composite can efficiently separate chloroform, toluene, petroleum ether, and n-hexane from water with excellent oil-water separation performance, with potential application in the environmental field.

Highly Efficient Cooperative Catalysis of Single-Site Lewis Acid and Brønsted Acid in a Metal-Organic Framework for the Biginelli Reaction.

A unique 3D framework containing three different types of nanoscale polyhedron cages was constructed by incorporating dinuclear [M2(µ2-OH)(COO)4] (M = Co, Ni) secondary building units and pyridyl-carboxylic-acid-supported tetracarboxylates. The assembled complexes possess isolated bifunctional single-site Lewis acid and Brønsted acid and can be used as highly efficient heterogeneous catalysts for the solvent-free Biginelli reaction with a high turnover frequency value of 338.4 h-1. Interestingly, a variety of 3,4-dihydropyrimidin-2(1 H)-ones have been obtained in high yields and short times.

Robust Bifunctional Core-Shell MOF@POP Catalyst for One-Pot Tandem Reaction.

A new bifunctional acid-base catalyst, core-shell UiO-66@SNW-1, with robust chemical and thermal stability, recyclability, and durable catalytic activity is synthesized by a convenient, universal strategy. Interestingly, this hybrid material can effectively catalyze deacetalization-Knoevenagel condensation reaction in the presence of excellent compartmentalization to spatially isolate opposing acid-base sites.

Palladium Nanoparticles Encapsulated in the MIL-101-Catalyzed One-Pot Reaction of Alcohol Oxidation and Aldimine Condensation.

A bifunctional catalyst, Pd nanoparticles (NPs) encapsulated in MIL-101, has been synthesized by capillary impregnation. The as-prepared Pd@MIL-101 was characterized by powder X-ray diffraction, N2 physisorption, X-ray photoelectron spectroscopy, transmission electron microscopy, and high-angle annular dark field scanning transmission electron microscopy, indicating that Pd NPs were highly dispersed in the pores of MIL-101 without deposition of the nanoparticles on the external surface or aggregation. The bifunctional catalyst of Pd@MIL-101 exhibited highly catalytic activity for alcohol oxidation and aldimine condensation one-pot reactions, where Pd NPs affords good oxidation activity and MIL-101 offers Lewis acidity. In particular, Pd@MIL-101 yielded an effective catalytic performance with toluene as the solvent, K2CO3 as the co-catalyst, and 353 K as the optimum reaction temperature for the one-pot reaction. After five cycles of reuse, Pd@MIL-101 still shows high catalytic performance. Above all, it is found that the enhanced catalytic performance was achieved via the synergistic cooperation of MIL-101 and Pd NPs.

Robust Bifunctional Lanthanide Cluster Based Metal-Organic Frameworks (MOFs) for Tandem Deacetalization-Knoevenagel Reaction.

A series of 12-connected lanthanide cluster based metal-organic frameworks (MOFs) have been constructed by [Ln6(µ3-OH)8(COO-)12] secondary building units (SBUs) and 2-aminobenzenedicarboxylate (BDC-NH2) ligands. These obtained materials exhibit high chemical stability and generic thermal stability, especially in acidic and basic conditions. They also present commendable CO2 adsorption capacity, and Yb-BDC-NH2 was further confirmed by a breakthrough experiment under both dry and wet conditions. Moreover, these materials possess both Lewis acid and Brønsted base sites that can catalyze one-pot tandem deacetalization-Knoevenagel condensation reactions.

Microporous Hexanuclear Ln(III) Cluster-Based Metal-Organic Frameworks: Color Tunability for Barcode Application and Selective Removal of Methylene Blue.

Two hexanuclear Ln(III) cluster-based metal-organic frameworks (MOFs) (Ln = Tb or Eu) and a series of isomorphic bimetallic Ln(III)-MOFs have been synthesized by changing the ratio of Tb(III) and Eu(III) under solvothermal conditions. The excellent linear color tunability (from green to red) makes them suitable for barcode application. In addition, the anionic Ln(III)-MOFs exhibit superior uptake capacity toward methylene blue (MB+) by an ion-exchange process, and its reversible adsorption performance makes 1 suitable for removal of organic dye MB+. The as-prepared anionic hexanuclear Ln(III) cluster-based MOFs can serve as a multifunctional material for an optical and environmental area.

Exceptionally Robust In-Based Metal-Organic Framework for Highly Efficient Carbon Dioxide Capture and Conversion.

An In-based metal-organic framework, with 1D nanotubular open channels, In2(OH)(btc)(Hbtc)0.4(L)0.6·3H2O (1), has been synthesized via an in situ ligand reaction, in which 1,2,4-H3btc is partially transformed into the L ligand. Compound 1 exhibits exceptional thermal and chemical stability, especially in water or acidic media. The activated 1 presents highly selective sorption of carbon dioxide (CO2) over dinitrogen. Interestingly, diffuse-reflectance infrared Fourier transform spectroscopy with a carbon monoxide probe molecule demonstrates that both Lewis and Brønsted acid sites are involved in compound 1. As a result, as a heterogeneous Lewis and Brønsted acid bifunctional catalyst, 1 possesses excellent activity and recyclability for chemical fixation of CO2 coupling with epoxides into cyclic carbonates under mild conditions. In addition, the mechanism for the CO2 cycloaddition reaction has also been discussed.

Robust molecular bowl-based metal-organic frameworks with open metal sites: size modulation to increase the catalytic activity.

Herein, two stable lead(II) molecular-bowl-based metal-organic frameworks and their micro- and nanosized forms with open metal sites were presented. These materials could act as Lewis acid catalysts to cyanosilylation reaction. Moreover, the catalytic performances are size-dependent, with the catalyst with nanosized form being 1 order of magnitude more efficient than those with micro- and millisized forms.

Defect engineering improves CO2/N2 and CH4/N2 separation performance of MOF-801.

A defect engineering modification method is reported to improve the CO2/N2 and CH4/N2 separation performance of MOF-801, owing to skeleton shrinkage caused by defect modification, Zr-FA0.5 shows excellent gas separation performance compared with the prototype MOF.

Superhydrophobic MOF/polymer composite with hierarchical porosity for boosting catalytic performance in an humid environment.

The poor hydrostability of most reported metal-organic frameworks (MOFs) has become a daunting challenge in their practical applications. Recently, MOFs combined with multifunctional polymers can act as a functional platform and exhibit unique catalytic performance; they can not only inherit the outstanding properties of the two components but also offer unique synergistic effects. Herein, an original porous polymer-confined strategy has been developed to prepare a superhydrophobic MOF composite to significantly enhance its moisture or water resistance. The selective nucleation and growth of MOF nanocrystals confined in the pore of PDVB-vim are closely related to the structure-directing and coordination-modulating properties of PDVB-vim. The resultant MOF/PDVB-vim composite not only produces superior superhydrophobicity without significantly disturbing the original features but also exhibits a novel catalytic activity in the Friedel-Crafts alkylation reaction of indoles with trans-ß-nitrostyrene because of the accessible sites and synergistic effects.

Superhydrophobic MOFs with enhanced catalytic activity for chemical fixation of CO2.

A general approach to prepare superhydrophobic MOFs (denoted as MOFs-CF3) through a post-decorating strategy for highly efficient chemical fixation of CO2 was demonstrated. The enhanced catalytic activity of MOFs-CF3 is attributed to a synergistic effect between the Lewis acid sites of MOFs and modification of the electron-withdrawing trifluoromethyl group, which resulted in a high CO2 enrichment capacity. The possible mechanism of cycloaddition catalyzed by the MOFs-CF3 catalyst was also proposed.

Mn(II)-based porous metal-organic framework showing metamagnetic properties and high hydrogen adsorption at low pressure.

A Mn(II)-based homometallic porous metal-organic framework, Mn(5)(btac)(4)(µ(3)-OH)(2)(EtOH)(2)·DMF·3EtOH·3H(2)O (1, btac = benzotriazole-5-carboxylate), has been solvothermally synthesized and structurally characterized by elemental analysis, thermogravimetric analysis, and X-ray crystallographic study. 1 is a 3D neutral framework featuring 1D porous channels constructed by {Mn-OH-Mn}(n) chains and btac linkers. Magnetic studies show that 1 is a 3D metamagnet containing 1D {Mn-OH-Mn}(n) ferrimagnetic chains. High-pressure H(2) adsorption measurement at 77 K reveals that activated 1 can absorb 0.99 wt % H(2) at 0.5 atm and reaches a maximum of 1.03 wt % at 5.5 atm. The steep H(2) absorption at lower pressure (98.2% of the storage capacity at 0.5 atm) is higher than the corresponding values of some MOFs (MIL-100 (16.1%), MOF-177 (57.1%), and MOF-5 (22.2%)). Furthermore, activated 1 can adsorb CO(2) at room temperature and 275 K. The adsorption enthalpy is 22.0 kJ mol(-1), which reveals the high binding ability for CO(2). Detailed gas sorption implies that the exposed Mn(II) coordination sites in the activated 1 play an important role to improve its adsorption capacities.

Bis-(di-methylamine-κN)bis[4-(1,2,4-triazol-1-yl)benzoato-κO]copper(II).

In the title compound, [Cu(C9H6N3O2)2(C2H7N)2], the Cu2+ cation is situated on an inversion center and is coordinated by the N atoms of two di-methyl-amine ligands and the carboxyl-ate O atoms of two 4-(1,2,4-triazol-1-yl)benzoate anions, leading to a slightly distorted square-planar N2O2 coordination environment. In the crystal, inter-molecular N-H⋯N hydrogen bonds between the amine function and the central N atom of the triazole ring lead to the formation of ribbons parallel to [11]. Weak inter-molecular C-H⋯O hydrogen-bonding inter-actions are also observed that consolidate the crystal packing.

A [(M2)6L8] metal-organic polyhedron with high CO2 uptake and efficient chemical conversion of CO2 under ambient conditions.

A new metal-organic polyhedron with a high surface area of 407 m2 g-1, possessing high CO2 uptake, is reported, which is synthesized using 4-connected Cu2(CO2)4 paddle-wheel moieties and 3-connected semi-rigid tripodal carboxylates. This material possesses a high density of Cu(II) Lewis acidic sites and demonstrates excellent performance as a heterogeneous catalyst for the chemical fixation of CO2 into cyclic carbonates under ambient conditions.