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Chemoselective reduction of nitroarenes to arylamines is a core technology for the synthesis of numerous chemicals. The technology, however, relies on applying precious noble metal catalysts. We present our findings on the development of robust nanoporous covalent triazine frameworks (CTFs) as metal-free catalysts for the green chemoselective reduction of nitroarenes. The turnover frequency is found to be 43.03 h

An important challenge in the valorization of CO2 and H2 into fuels is the development of a stable, reusable and easy to handle heterogeneous catalyst. Here, a silica nanofibrous membrane is investigated as carrier for Ru nanoparticles, themselves encapsulated inside the metal organic framework (MOF) Cr-MIL-101. The catalytic membrane is investigated for the Sabatier methanation reaction. The direct electrospinning of a tetraorthosilicate (TEOS) sol results in a highly thermal resistant silica nanofibrous structure (up to 1100 °C) with pores between the fibers in the µm-range, allowing a high gas throughput with low pressure requirements. A straightforward dip-coating procedure of the carrier was used to obtain a Ru@MIL-101 functionalized silica nanofibrous veil, avoiding Ru clustering. The obtained catalytic membrane exhibited an apparent turnover frequency of 3257 h-1 at 250 °C. This system therefore paves the way towards structured reactors for efficient CO2 hydrogenation processes.

As two newly emerging classes of highly porous compounds, metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), introduced in 1999 and 2005 respectively, have shown promising results for several applications. These materials are now being extensively studied and explored by both academic and industrial scientists as a result of their distinctive properties. Both materials have the advantages of structural tuneability, diversity and high porosity that endow them with tremendous possibilities for multiple applications. The countless combination of building units (metal ions and organic linkers) offers immense structural properties to obtain advanced porous materials. Still, the structural design and advanced applications of these materials are relatively unexplored and deserve further investigation. This review represents the recent development of MOFs and COFs from their syntheses and structural properties to enhanced applications. The unique possibility to introduce a wide range of functionalities to the framework of the materials is comprehensively investigated. We further describe the catalytic sites in MOFs and COFs ranging from metal-free COFs as highly active catalysts to metal-decorated MOFs and COFs. An emphasized application of MOFs/COFs as efficient catalysts is oxidative reactions which is regarded as a crucial transformation in organic synthesis.

The reaction of pyridine-2,4-dicarboxylic acid (2,4-H2 pydc) with Ce(NO3)3·6H2O, by applying only minor changes to the reaction conditions, generated a series of new one-, two-, and three-dimension...

The sequential/cyclic adsorption plasma catalysis (APC) systems have been widely investigated to remove low concentrations (< 1000 ppm) of VOCs from a huge volume of exhaust gas to reduce the energy cost 1,2 . In APC, the VOC is first adsorbed on the adsorbent and/or catalyst (plasma off) after which it is converted to CO 2 by NTP (plasma on). In this study, an APC system consisting of a dielectric barrier discharge (DBD) reactor packed with MO x /MS-13X (M = Cu, Mn, or Cu-Mn) and glass beads was investigated for the abatement of toluene in dry air. The total amount of adsorbed toluene, the catalytic performance of MO x /MS-13X, the energy cost and the energy yield of the APC process were investigated for the different metal loaded MS-13X. Results revealed that the all metal loadings on MS-13X enhanced the mineralization efficiency and reduced the energy cost to remedy 1 m 3 of air when compared to unloaded MS-13X. The lowest energy cost (0.25 kWh.m -3 ) and highest energy yield (4.37 g/kWh) were obtained using CuMnO x /MS-13X. Then, the influence of the amount of toluene initially adsorbed on CuMnO x /MS-13X on the mineralization efficiency of the APC process was also studied. In addition, the stability and regenerability of the CuMnO x /MS-13X catalyst was examined during 4 cycles of APC by comparing (i) the amount of adsorbed toluene, (ii) the breakthrough time, (iii) the carbon balance and (iv) the bulk and surface properties of fresh and NTP regenerated CuMnO x /MS-13X. It was observed that the crystallinity, textural properties, and elemental composition of the CuMnO x /MS-13X zeolite as well as the oxidation state of the metals loaded on MS-13X did not change upon NTP exposure.

Herein, a highly N-rich covalent triazine framework (CTF) is applied as support for a RuIII complex. The bipyridine sites within the CTF provide excellent anchoring points for the [Ru(acac)2(CH3CN)2]PF6 complex. The obtained robust RuIII@bipy-CTF material was applied for the selective tandem aerobic oxidation–Knoevenagel condensation reaction. The presented system shows a high catalytic performance (&gt, 80% conversion of alcohols to α, β-unsaturated nitriles) without the use of expensive noble metals. The bipy-CTF not only acts as the catalyst support but also provides the active sites for both aerobic oxidation and Knoevenagel condensation reactions. This work highlights a new perspective for the development of highly efficient and robust heterogeneous catalysts applying CTFs for cascade catalysis.

Crystalline covalent triazine frameworks (CTFs) with intrinsic porosity and high stability are an excellent platform for engineering luminescence properties, as their building blocks and guest ions are all important factors in light emission. Herein, a highly crystalline bipyridine-based CTF (Bipy-CTF) is synthesized under mild conditions. The controlled tethering of lanthanide ions (Ln = Eu3+ and Tb3+) onto Bipy-CTF combined with selective photoexcitation results in a ratiometric luminescent thermometer (LnCTF). This LnCTF thermometer exhibits an excellent linear response in the solid state over a wide range of temperatures (200–340 K), with a temperature uncertainty below 0.2% and very good reusability (up to 98.5% repeatability). Moreover, the suspended material in water shows a temperature sensitivity down to 253 K (−20 °C), which is a very important finding for monitoring the physiological processes within biological and biochemical systems during freezing/defrosting treatment with precise temperature measurements. We also studied and confirmed the low cytotoxicity of the LnCTF towards cells thereby opening prospects for future in vivo applications. This work thus highlights a new application of LnCTF materials as ratiometric luminescent molecular thermometers with excellent sensitivity in the physiological temperature range.

Given the complex calcified nature of the fibrous bone tissue, a combinatorial approach merging specific topographical/biochemical cues was adopted to design bone tissue-engineered scaffolds. Coral having a Ca-enriched structure was added to electrospun chitosan (CS)/polyethylene oxide (PEO) nanofibers that were subjected to plasma surface modifications using a medium pressure Ar, air or N2 dielectric barrier discharge. Plasma incorporated oxygen- and nitrogen-containing functionalities onto the nanofibers surface thus enhancing their wettability. Plasma treatment enhanced the performance of osteoblasts and the interplay between plasma treatment and coral was shown to boost initial cell adhesion. The fibers capacity to trigger calcium phosphate growth was predicted via immersion in simulated body fluid. Globular carbonate apatite nanocrystals were deposited on plasma-treated CS/PEO NFs while thicker layers of flake-like nanocrystals were covering plasma-treated Coral/CS/PEO fibers without blocking the interfibrous pores. Overall, the exclusive multifaceted plasma-treated Coral/CS/PEO nanofibers are believed to revolutionize the bone tissue engineering field.

Low-cost metal-free catalysts enable O2 activation as a key step in many important sustainable processes., Oxygen activation is a critical step in ubiquitous heterogeneous oxidative processes, most prominently in catalysis, electrolysis, and pharmaceutical applications. We present here our findings on metal-free O2 activation on covalent triazine frameworks (CTFs) as an important class of N-rich materials. The O2 activation process was studied for the formation of aldehydes, ketones and imines. A detailed mechanistic study of O2 activation and the role of nitrogen heteroatoms were comprehensively investigated. The electron paramagnetic resonance (EPR) and control experiments provide strong evidence for the reaction mechanism proving the applicability of the CTFs to activate oxygen into superoxide species. This report highlights the importance of a self-templating procedure to introduce N functionalities for the development of metal-free catalytic materials. The presented findings reveal an important step toward the use of CTFs as inexpensive and high-performance alternatives to metal-based materials not only for catalysis but also for biorelated applications dealing with O2 activation.

Reaction of α-keto stabilized sulfur ylide (Me)2SCHC(O)C6H4-p-CN (Y) with HgX2 (X = Cl, Br and I) led to the formation of new dinuclear products of the type [HgX2(Y)]2 (X = Cl (1), Br (2) and I (3)). Furthermore, the reaction of the corresponding sulfur ylide (Y) with Hg(NO3)2·H2O in equimolar ratio, using methanol as a solvent, was shown to produce the polynuclear complex [(Y)Hg(NO3)2]n (4). The obtained compounds were characterized using elemental analysis, IR, 1H and 13C NMR techniques. The structures of compounds Y and 1 were characterized by single-crystal X-ray diffraction analysis. Also, in order to confirm the crystalline nature of complexes 1-3, powder X-ray diffraction (XRD) pattern was used. Likewise, the antioxidant property of the complexes was examined by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging which revealed the strong-to-moderate radical scavenging ability (IC50; 0.163 ± 0.004 to 0.936 ± 0.012 mg·mL−1) of the synthesized compounds. Further, results from this study indicated that the compounds possess moderate antibacterial activity.

The reactions of α-keto stabilized phosphorus ylide Ph2P(CH2)2PPh2C(H)C(O)C6H4-m-Br (Y) with [MCl2(cod)] (M = Pd or Pt; cod = 1,5-cyclooctadiene) in equimolar ratio using dichloromethane as a solvent are reported. These reactions led to the formation of new P, C-chelated pallada- and platinacycle complexes [MCl2(Ph2P(CH2)2PPh2C(H)C(O)C6H4-m-Br)] (M = Pd (C1) and Pt (C2)). Characterization of the obtained compounds was performed by elemental analysis and IR, 1H, 13C, and 31P NMR spectroscopic methods. Also, the unequivocal structures of these complexes were characterized crystallographically. Both structures consist of six-membered rings formed by coordination of the phosphorus ylide (Y) through the phosphine group and the ylidic carbon atom to the metal center. Furthermore, palladacycle C1 was employed as an efficient catalyst in the Mizoroki-Heck coupling reaction of several aryl chlorides and olefins. The coupled products of these reactions were obtained under aerobic conditions in high yields using aqueous DMF as a solvent. Additionally, the antioxidant capacity of the reported compounds with butylated hydroxytoluene (BHT) as standard was evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method. Apparently, all synthesized compounds possess strong antioxidant capacity (IC50; 0.584 ± 0.009–0.751 ± 0.003 mg/ml).

A treatment of piperazine (H2pipz) and pyridine-2,6-dicarboxylic acid (H2pydc) with CeIII ion led to the formation of a new binuclear cerium(III) complex (H2pipz)[Ce2(pydc)4(H2O)4]·(H2O) (1). Compound 1 was characterized by elemental analyses, IR spectroscopy, thermal gravimetric and single crystal X-ray diffraction. The binuclear unit of 1 contains CeIII cations bridged by two anionic pydc2− ligands. The Cerium(III) ion is nine-coordinated by seven oxygen atoms from two water molecules and five carboxylate groups, and two nitrogen atoms from two pydc2− ligands. Non-covalent interactions i.e. hydrogen bonds are present in the crystal structure of 1 and assemble the binuclear units and the co-crystallized water and piperazine molecules into a 3D architecture. Compound 1 was used for the preparation of the CeO2 nanoparticles. Synthesized CeO2 nanoparticles were characterized by IR spectroscopy, powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). Furthermore, the solid-state luminescent properties of compound 1 at room temperature were studied.

A copper-containing polyoxovanadate nanocluster, [(C2H5)4N]4[V8Cu2O24]∙2H2O (1), was synthesized through reaction between the Cu(NO3)2∙3H2O and [(C2H5)4N]4VO3 in the molar ratio 1 : 4. Nanocluster ...

Synergistic catalysis holds great promise to enhance the catalytic performance of heterogeneous catalysts suffering from sluggish reaction kinetics. Much effort has been dedicated to the development of bimetallic systems in which the two promoter elements display synergistic benefits compared to monometallic counterparts. However, the use of bimetallic catalysts inescapably raises the cost of preparation and environmental issues. This study discovers a synergistic effect when using a bipyridine covalent triazine framework (bipy-CTF) as support for an IrIII complex in the aerobic oxidation reaction. The detailed mechanistic study provides insights into the function of the bipy-CTF in this synergistic catalysis. The EPR and in-situ XANES analyses confirm the applicability of bipy-CTF to activate oxygen and alcohol, resulting in an enhancement of the performance of the IrIII complex to exceed the activity of the homogeneous counterpart. This is an unprecedented report on promoting the activity of a heterogeneous catalyst through its solid support.

International audience; Mixed-metal MOFs are metal–organic frameworks that contain at least 2 different metal ions as nodes of their frameworks. They are prepared relatively easily by either a one-pot synthesis with a synthesis mixture containing the different metals, or by a post-synthetic ion-exchange method by soaking a monometallic MOF in a concentrated solution of a different (but compatible) metal-ion. More difficult is the accurate characterization of these materials. Is the formed product a mixture of monometallic MOFs or indeed a MOF with different metallic nodes? Are the metals randomly distributed or do they form domains? What is the oxidation state of the metals? How do the metals mutually influence each other, and impact the material's performance? Advanced characterization techniques are required e.g. X-ray absorption spectroscopy, magnetic resonance and electron microscopy. Computational tools at multiple scales are also often applied. In almost every case, a judicious choice of several techniques is required to unambiguously characterize the mixed-metal MOF. Although still in their infancy, several applications are emerging for mixed-metal MOFs, that improve on conventional monometallic MOFs. In the field of gas sorption and storage, especially the stability and affinity towards the target gases can be largely improved by introducing a second metal ion. In the case of flexible MOFs, the breathing behavior, and in particular the pressure at which the MOF opens, can be tailored. In heterogeneous catalysis, new cascade and tandem reactions become possible, with particular focus on reactions where the two metals in close proximity truly form a mixed-metal transition state. The bimetallic MOF should have a clear benefit over a mixture of the respective monometallic MOFs, and bimetallic enzymes can be a huge source of inspiration in this field. Another very promising application lies in the fields of luminescence and sensing. By tuning the lanthanide metals in mixed-metal lanthanide MOFs and by using the organic linkers as antennae, novel smart materials can be developed, acting as sensors and as thermochromic thermometers. Of course there are also still open challenges, as also mixed-metal MOFs do not escape the typical drawbacks of MOFs, such as low stability in moisture and possible metal leaching in liquids. The ease of synthesis of mixed-metal MOFs is a large bonus. In this critical review, we discuss in detail the synthesis, characterization, computational work and applications of mixed-metal MOFs.

In this study, we present for the first time the immobilization of phosphotungstic acid (H3PW12O40, HPW) into the nanocages of a dual amino-functionalized ionic liquid (DAIL)-modified MIL-101(Cr) framework under mild conditions. The obtained PW/DAIL/MIL-101(Cr) was evaluated as a catalyst in the oxidation of benzyl alcohol using TBHP in chloroform. In order to obtain insights into the role of the DAIL during catalysis, a DAIL-free catalyst (HPW/MIL-101(Cr)) was also prepared. Both catalysts were fully characterized using several techniques. In comparison with the HPW/MIL-101(Cr) material, PW/DAIL/MIL-101(Cr) showed an enhanced catalytic performance in the selective oxidation of benzyl alcohol. This was mainly attributed to the ability of the DAIL groups to form hydrogen bonds, thus enhancing the accessibility of TBHP. Furthermore, the immobilization of the DAIL groups onto MIL-101(Cr) resulted in increased thermal stability of the obtained PW/DAIL/MIL-101(Cr) which showed stability up to 400 °C. Moreover, the PW/DAIL/MIL-101(Cr) catalyst exhibited good recyclability and selectivity. The catalyst could be reused for at least five cycles with no significant leaching of the tungsten species or loss of crystallinity and activity.

The heterogenization of an Ir-III complex is accomplished by the modification of a nanoporous Ga-based metal-organic framework ( MOF), denoted as COMOC-4. The introduction of the Ir complex was performed successfully through two different strategies ( post-and prefunctionalization). The obtained Irbased MOF materials were compared in terms of the Ir loading, specific surface area, and crystallinity. In this case, the prefunctionalization approach was a powerful way to obtain a high Ir loading and surface area and preserve the formation of the de-sired MOF topology. The (IrCp)-Cp-III*Cl-COMOC-4 ( Cp*= 1,2,3,4,5-pentamethylcyclopentadienyl) material exhibits a good catalytic performance in the oxidation of benzyl alcohol using O-2 as a clean oxidant. Furthermore, the stability and reusability were examined and showed that the (IrCp)-Cp-III*Cl-COMOC-4 material could be reused for at least four cycles with no decrease in activity and selectivity. Additionally, no significant leaching of the Ir and Ga species or loss of the crystallinity was observed.

Using a sonochemical method, nanoparticles of a new Ce(III) supramolecular compound, (NAMH(+))2[Ce4(pydc)6(pydcH)2(H2O)8]·8H2O (1), (H2pydc=2,6-pyridinedicarboxylic acid, NAM=nicotinamide), have been synthesized. Compound 1 was characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), FT-IR spectroscopy and elemental analyses, and its structure was determined by X-ray crystallography. It has been revealed that its structure consists of tetra-nuclear building units that extend to a 3D supramolecular network via non-covalent interactions mainly hydrogen bonding. The thermal stability of complex 1 both for its crystals and nanostructures has been studied by the thermal gravimetric (TG) method and compared with each other. The role of ultrasound irradiation power and the concentration of initial reactants on the size and morphology of the nano-structured complex 1, has been investigated. Ceria nanoparticles were obtained upon the calcination of complex 1 at 800°C under atmospheric air. Furthermore, the fluorescent properties of complex 1 at room temperature were studied.

The luminescence properties of two series of heteronuclear lanthanide-based coordination polymers were studied. The heteronuclear compounds were synthesized via mechanosynthesis routes. These series have the general chemical formula [Ln1−xLn′x(pzdc)(Hpzdc)(H2O)3]n (Ln = La3+ or Ce3+, Ln′ = Sm3+, Eu3+, Tb3+, or Dy3+, x = 0.050, 0.075 or 0.100) where H2pzdc stands for 2,3-pyrazinedicarboxylic acid (Hpzdc− = mono-deprotonated and pzdc2− = bis-deprotonated). The heteronuclear compounds that belong to each series are isostructural to a new two-dimensional La(III) coordination polymer and to an already reported homonuclear two-dimensional Ce(III) coordination polymer, [La(pzdc)(Hpzdc)(H2O)3]n and [Ce(pzdc)(Hpzdc)(H2O)3]n, respectively. These two crystal structures are isostructural as well. The La(III) and Ce(III) compounds have been synthesized via conventional heating and mechanosynthesis. The La(III) coordination polymer was structurally characterized by single crystal X-ray diffraction and was shown to consist of 2D sheets that construct a three-dimensional supramolecular architecture via non-covalent interactions i.e. hydrogen bonding. To find the optimal lanthanide-ion concentrations, the systems were doped with 5%, 7.5% or 10% of a spectroscopically active ion (Sm3+, Eu3+, Tb3+, or Dy3+) to investigate the luminescence properties.

Nanoparticles of a new two-dimensional cerium(III) coordination polymer compound, [Ce(pzdc)(pzdcH)(H2O)3]n (1), (H2pzdc = 2,3-pyrazinedicarboxylic acid), have been synthesized by a sonochemical process and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), FT-IR spectroscopy and elemental analyses. Compound 1 was structurally characterized by single crystal X-ray diffraction and was shown that it consists of 2D sheets that construct a three-dimensional supramolecular architecture via non-covalent interactions i.e. hydrogen bonding. The thermal stability of compound 1 both for its crystals and nanostructures has been studied by the thermal gravimetric (TG) method and compared with each other. The role of ultrasound irradiation power and the concentration of initial reactants on the size and morphology of the nano-structured compound 1, has been investigated. Calcination of compound 1 at 800 °C under air atmosphere yields ceria nanoparticles. Furthermore, the fluorescent properties of compound 1 at room temperature were studied.

A five-coordinated Fe(III) complex with the distorted trigonal bipyramidal configuration was synthesized by reactions of FeCl3⋅6H2O and 2-(2′-hydroxyphenyl)oxazoline (Hphox) as a bidentate O N donor oxazoline ligand. Complex [Fe(phox)2Cl] was fully characterized, including by single-crystal X-ray structure analysis. DFT calculations were accompanied with experimental results in order to obtain a deeper insight into the electronic structure and vibrational normal modes of complex. Oxidation of sulfides to sulfoxides in one-step was conducted by this complex as catalyst using urea hydrogen peroxide (UHP) in mixture of CH2Cl2/CH3OH (1:1) under air at room temperature. The results show that using this system in oxidation of sulfides, sulfoxides are obtained as the main products, together with variable amounts of sulfones (⩽13%), depending on the nature of the substrate.

A new mononuclear molybdenum(VI)–oxodiperoxo complex [MoO(O2)2(phox)] with a simple bidentate ligand, 2-(2′-hydroxyphenyl)-5,6-dihydro-1,3-oxazine (Hphox), has been synthesized and characterized by X-ray structure analysis, elemental analysis, infrared, and 1H NMR spectroscopy. A triclinic space group P-1 was determined by X-ray crystallography from single-crystal data of this complex. The resulting complex functioned as a facile sulfide oxidation catalyst with urea hydrogen peroxide as terminal oxidant at room temperature. The catalyst showed efficient reactivity in oxidation of sulfides giving high yield and selectivity.

The glucose-based ligand, N-salicylidene-d-glucosamine (Sal-d-glsmN), was readily obtained by reaction of salicylaldehyde (Hsal) with the d-glucosamine hydrochloride. Ligand Sal-d-glsmN was found to be an efficient ligand in the palladium-catalyzed Suzuki and Heck C–C coupling reactions in aqueous medium under aerobic condition. It was found that the use of Sal-d-glsmN/Pd(OAc)2 system as a catalyst, aryl halides undergo Suzuki and Heck cross-couplings, respectively, with arylboronic acids and olefins to give the desired products in moderate to excellent yields.

We have evaluated the catalytic activity of a molybdenum(VI) oxo–peroxo complex through the oxidation and reduction of sulfur-based compounds. Arylalkyl, diaryl and dialkyl sulfides are selectively oxidized to corresponding sulfoxides, with tert -butyl hydroperoxide (TBHP), in the presence of MoO(O 2 )(phox) 2 complex as catalyst. This molybdenum complex was also found to be an efficient catalyst for the deoxygenation of sulfoxides to sulfides with PPh 3 in excellent yields and chemoselectivity.

The reaction of alpha-keto-stabilized diphosphine ylides [Ph2P(CH2)(n)PPh2C(H)C(O)C6H4-p-CN] (n = 1 (Y-1); n = 2 (Y-2)) with dibromo(1,5-cyclooctadiene) palladium(II)/platinum(II) complexes, [Pd/PtBr2(cod)], in equimolar ratio gave the new cyclometalated Pd(II) and Pt(II) complexes [Br2Pd(kappa(2)-Y-1)] (1), [Br2Pt(kappa(2)-Y-1)] (2), [Br2Pd(kappa(2)-Y-2)] (3) and [Br2Pt(kappa(2)-Y-2)] (4). These compounds were screened in a search for novel antibacterial agents and characterized successfully using Fourier transfer infrared and NMR (H-1, C-13 and P-31) spectroscopic methods. Also, the structures of complexes 1 and 2 were characterized using X-ray crystallography. The results showed that the P,C-chelated complexes 1 and 2 have structures consisting of five-membered rings, while 3 and 4 have six-membered rings, formed by coordination of the ligand through the phosphine group and the ylidic carbon atom to the metal centre. Also, a theoretical study of the structures of complexes 1-4 was conducted at the BP86/def2-SVP level of theory. The nature of metal-ligand bonds in the complexes was investigated using energy decomposition analyses (EDA) and extended transition state combined with natural orbitals for chemical valence analyses. The results of EDA confirmed that the main portions of Delta E-int, about 57-58%, in the complexes are allocated to Delta E-elstat.