The search for simple, earth-abundant, cheap, and nontoxic metal catalysts able to perform industrial hydrogenations is a topic of interest, transversal to many catalytic processes. Here, we show ...that isolated FeIII–O sites on solids are able to dissociate and chemoselectively transfer H2 to acetylene in an industrial process. For that, a novel, robust, and highly crystalline metal–organic framework (MOF), embedding FeIII–OH2 single sites within its pores, was prepared in multigram scale and used as an efficient catalyst for the hydrogenation of 1% acetylene in ethylene streams under front-end conditions. Cutting-edge X-ray crystallography allowed the resolution of the crystal structure and snapshotted the single-atom nature of the catalytic FeIII–O site. Translation of the active site concept to even more robust and inexpensive titania and zirconia supports enabled the industrially relevant hydrogenation of acetylene with similar activity to the Pd-catalyzed process.
•Impressive potential of the metallosupramolecular strategy for molecular spintronics.•Exchange-coupled, electro- and photoactive dicopper(II) metallacyclophanes as targets.•Models for the ...fundamental research on through-ligand EE interaction.•Molecular components to build a metal-based spintronic circuit.•Candidates for the study of electron transport through single molecules.
The work presented in this review constitutes a successful extension of our group's research on the chemistry and physics of dinuclear copper(II) metallacyclophanes with aromatic polyoxalamide ligands. The design and synthesis of metallacyclic complexes that contain multiple electro- and photoactive (either metal- or ligand-based) spin carriers and the study of their spectroscopic and magnetic properties as well as their redox and photochemical activity are of large interest in the multidisciplinary field of metallosupramolecular chemistry. In doing this, a ligand design approach has been followed which is based on the copper(II)-mediated self-assembly of bis(oxamato) bridging ligands possessing potentially electro- and photoactive, extended π-conjugated aromatic spacers. This strategy benefits from the inherent physical and chemical properties of aromatic organic molecules by functionalizing them with two oxamato donor groups to get dinucleating ligands that are then able to self-assemble with square planar CuII ions affording the targeted oxamato-based dicopper(II) metallacyclophanes. The organic functionalization in this new class of metallacyclic systems constitutes a unique example of ligand design for the supramolecular control of the structure and magnetic properties, as well as the electro- and photochemical activities. This novel class of oxamato-based dicopper(II) metallacyclophanes provides excellent models for the fundamental study on through-ligand long-distance and redox- or photo-triggered electron exchange phenomena, which are two central topics in molecular magnetism and molecular electronics. Using these simple dinuclear metallacyclic complexes as dynamic chemical systems to perform specific and selective tasks under the control of an external (electro- and/or photochemical) stimulus that switches “ON” and “OFF” their electronic (optical and/or magnetic) properties may have an enormous impact in several domains of molecular nanoscience. Hence, oxamato-based dicopper(II) metallacyclophanes appear as very promising candidates to get multifunctional magnetic devices controlling and facilitating the spin communication (“molecular magnetic couplers” and “molecular magnetic wires”) or exhibiting charge storage (“molecular magnetic capacitors”) and bistable spin behavior (“molecular magnetic rectifiers” and “molecular magnetic switches”) for potential applications in information processing and storage in the emerging areas of molecular spintronics and quantum computing. Moreover, because of the potential high affinity for a variety of metal surfaces through the free carbonyl-oxygen atoms of the oxamate groups, they are very appealing candidates for the study of coherent electron transport through single molecules.
The impressive potential of the metallosupramolecular approach in designing new functional magnetic materials constitutes a great scientific challenge for the chemical research community that ...requires an interdisciplinary collaboration. New fundamental concepts and future applications in nanoscience and nanotechnology will emerge from the study of magnetism as a supramolecular function in metallosupramolecular chemistry. Our recent work on the rich supramolecular coordination chemistry of a novel family of aromatic polyoxalamide (APOXA) ligands with first-row transition metal ions has allowed us to move one step further in the rational design of metallosupramolecular assemblies of increasing structural and magnetic complexity. Thus, we have taken advantage of the new developments of metallosupramolecular chemistry and, in particular, the molecular-programmed self-assembly methods that exploit the coordination preferences of paramagnetic metal ions and suitable designed polytopic ligands. The resulting self-assembled di- and trinuclear metallacyclic complexes with APOXA ligands, either metallacyclophanes or metallacryptands, are indeed ideal model systems for the study of the electron exchange mechanism between paramagnetic metal centers through extended π-conjugated aromatic bridges. So, the influence of different factors such as the topology and conformation of the bridging ligand or the electronic configuration and magnetic anisotropy of the metal ion have been investigated in a systematic way. These oligonuclear metallacyclic complexes can be important in the development of a new class of molecular magnetic devices, such as molecular magnetic wires (MMWs) and switches (MMSs), which are major goals in the field of molecular electronics and spintronics. On the other hand, because of their metal binding capacity through the outer carbonyl-oxygen atoms of the oxamato groups, they can further be used as ligands, referred to as metal–organic ligands (MOLs), toward either coordinatively unsaturated metal complexes or fully solvated metal ions. This well-known “complex-as-ligand” approach affords a wide variety of high-nuclearity metal–organic clusters (MOCs) and high-dimensionality metal–organic polymers (MOPs). The judicious choice of the oligonuclear MOL, ranging from mono- to di- and trinuclear species, has allowed us to control the overall structure and magnetic properties of the final oxamato-bridged multidimensional (
nD,
n
=
0–3) MOCs and MOPs. The intercrossing between short- (nanoscopic) and long-range (macroscopic) magnetic behavior has been investigated in this unique family of oxamato-bridged metallosupramolecular magnetic materials expanding the examples of low-dimensional, single-molecule (SMMs) and single-chain (SCMs) magnets and high-dimensional, open-framework magnets (OFMs), which are brand-new targets in the field of molecular magnetism and materials science.
A bio-metal-organic framework (bio-MOF) derived from the amino acid L-serine has been prepared in bulk form and evaluated as sorbent for the molecular recognition and extraction of B-vitamins. The ...functional pores of bio-MOF exhibit high amounts of hydroxyl groups jointly directing other supramolecular host-guest interactions thus providing the recognition of B-vitamins in fruit juices and energy drinks. Single-crystal X-ray diffraction studies reveal the specific B-vitamin binding sites and the existence of multiple hydrogen bonds between these target molecules and the framework. It offered unique snapshots to accomplish an efficient capture of these solutes in complex aqueous matrices. Four B-vitamins (thiamin, nicotinic acid, nicotinamide, and pyridoxine) were investigated. They were eluted from the sorbent with phosphate buffer at pH 7 and analyzed by HPLC with UV detection. The sorbent was compared with commercial C18 cartridges. Following the procedure, acceptable reproducibility (RSD values < 14%) was achieved, and the detection limits were in the range 0.4 to 1.4 ng mL
−1
. The method was applied to the analysis of energy drink and juice samples and the recoveries were between 75 and 123% in spiked beverage samples.
Graphical abstract
A bio-MOF as SPE sorbent was prepared and applied to the extraction of B-vitamins in fruit juices and energy drinks.
Ferroelectrics (FEs) are materials of paramount importance with a wide diversity of applications. Herein, we propose a postsynthetic methodology for the smart implementation of ferroelectricity in ...chiral metal−organic frameworks (MOFs): following a single-crystal to single-crystal cation metathesis, the Ca2+ counterions of a preformed chiral MOF of formula Ca6 II{CuII 24(S,S)-hismox12(OH2)3}·212H2O (1), where hismox is a chiral ligand derived from the natural amino acid l-histidine, are replaced by CH3NH3 +. The resulting compound, (CH3NH3)12{CuII 24(S,S)-hismox12(OH2)3}·178H2O (2), retains the polar space group of 1 and is ferroelectric below 260 K. These results open a new synthetic avenue to enlarge the limited number of FE MOFs.
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•Coordination chemistry approach from molecular magnetism to molecular spintronics and quantum computation.•Electron exchange and double exchange in homo- and heterovalent dinuclear ...complexes.•Spin crossover and valence tautomerism in mono-, di- and tetranuclear complexes.•Magnetic anisotropy and spin dynamics in metal clusters and coordination polyhedra.•Spin dynamics and quantum coherence in mononuclear complexes and metal rings.
Molecular magnetism has travelled a long way from the pioneering studies on electron exchange and double exchange or spin crossover and valence tautomerism in small oligonuclear complexes, from mono- to di- and tetranuclear species, to the current investigations about magnetic anisotropy and spin dynamics or quantum coherence of simple mono- or large polynuclear complexes, behaving as switchable bistable molecular nanomagnets for potential applications in information data storage and processing. In this review, we focus on the origin and development of the research in the field of molecular magnetism from a coordination chemistry viewpoint, which dates back to the establishment of magnetochemistry as a novel discipline among the molecular sciences. This overview is conceived as an attempt to orientate coordination chemists regarding their role in the future direction that molecular magnetism will undergo in its further evolution toward molecular spintronics and quantum computation. A particular emphasis will be given to some selected recent advances in single-molecule spintronic circuitry and quantum computing devices based on the large class of multiresponsive and multifunctional magnetic metal complexes to stimulate the progress in the field of molecular magnetism.
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•Mixed-component MOFs are organised and described here in four main categories.•Mixed-component MOFs can improve MOFs' performance in a wide range of applications.•The main ...applications of Mixed-component MOFs are discussed in this work.•Mixed-component MOFs offer unique perspectives in enzymatic and metal cluster catalysis.
The synthesis of mixed-component metal-organic frameworks (MOFs) –including multivariate MOFs (MTV-MOFs), multicomponent MOFs, mixed-metals MOFs and mixed-ligands and metals MOFs– is becoming a very active research field. This is mainly based on the unique possibilities these materials offer to incorporate multiple functionalities and in how this heterogenity and complexity is translated in unexpected properties, which are not just the sum of each component. This review critically encompasses the progress made in this field, covering the synthetic approaches, and specially focusing on the current reported applications –such as gas storage and separation, catalysis, luminescence, conductivity, biological ones and water remediation. It also raises, as a perspective, some of the challenges the field has to overcome to reach their full-potential, and through two applications –(bio)enzymatic catalysis and synthesis of heterometallic subnanometric clusters and nanoparticles–, as exemplary cases, present some promising ways to take advantage of the intrinsic properties of mixed-components MOFs to make a breakthrough on the respective fields of application.
Mimicking enzymatic processes carried out by natural enzymes, which are highly efficient biocatalysts with key roles in living organisms, attracts much interest but constitutes a synthetic challenge. ...Biological metal–organic frameworks (bioMOFs) are potential candidates to be enzyme catalysis mimics, as they offer the possibility to combine biometals and biomolecules into open-framework porous structures capable of simulating the catalytic pockets of enzymes. In this work, we first study the catalase activity of a previously reported bioMOF, derived from the amino acid L-serine, with formula {CaIICuII 6(S,S)-serimox3(OH)2(H2O)} · 39H2O (1) (serimox = bis(S)-serineoxalyl diamide), which is indeed capable to mimic catalase enzymes, in charge of preventing cell oxidative damage by decomposing, efficiently, hydrogen peroxide to water and oxygen (2H2O2 → 2 H2O + O2). With these results in hand, we then prepared a new multivariate bioMOF (MTV-bioMOF) that combines two different types of bioligands derived from L-serine and L-histidine amino acids with formula CaIICuII 6(S,S)-serimox2(S,S)-hismox1(OH)2(H2O)}·27H2O (2) (hismox = bis(S)-histidineoxalyl diamide ligand). MTV-bioMOF 2 outperforms 1 degrading hydrogen peroxide, confirming the importance of the amino acid residue from the histidine amino acid acting as a nucleophile in the catalase degradation mechanism. Despite displaying a more modest catalytic behavior than other reported MOF composites, in which the catalase enzyme is immobilized inside the MOF, this work represents the first example of a MOF in which an attempt is made to replicate the active center of the catalase enzyme with its constituent elements and is capable of moderate catalytic activity.
By means of the facile chemistry, structural assembly, and transformation of four mononuclear Dy(III) complexes, Dy(bpad)3·CH3OH·H2O (1), Dy(bpad)2(H2O)2·NO3 (2), Dy(bpad)2(tmhd) (3), and ...Dy(bpad)2(btfa) (4) (Hbpad = N3-benzoylpyridine-2-carboxamidrazone, tmhd = 2,2,6,6-tetramethylheptane-3,5-dione, btfa = 3-benzoyl-1,1,1-trifluoroacetone), with distinct architectures and local symmetries were established. The disparity of the coordination geometries around the Dy(III) ion among these complexes impacts the strength of the crystal field and the local tensor of anisotropy (D) of each Dy site and their relative orientations, therefore giving rise to diverse SIM behaviors with distinguishing relaxation energy barriers of 106.93 K for 1, 52.55 K for 2, 48.16 K for 3, and 51.41 K for 4. The differences of the magnetic property and the magnetic anisotropy for four complexes have been explained by ab initio calculations, which are corresponding to the experimental results.
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