Two-dimensional Metal-organic Networks Research Articles

Construction of Two-Dimensional Organometallic Coordination Networks with Both Organic Kagome and Semiregular Metal Lattices on Au(111).

Two-dimensional metal-organic networks (2D MONs) having heterogeneous coordination nodes (HCNs) could exhibit excellent performance in catalysis and optoelectronics because of the unbalanced electron distribution of the coordinating metals. Therefore, the design and construction of 2D MONs with HCNs are highly desirable but remain challenging. Here, we report the construction of 2D organometallic coordination networks with an organic Kagome lattice and a semiregular metal lattice on Au(111) via the in situ formation of HCNs. Using a bifunctional precursor 1,4-dibromo-2,5-diisocyanobenzene, the coordination of isocyano with Au adatom on a room-temperature Au(111) yielded metal-organic coordination chains with isocyano-Au-isocyano nodes. In contrast, on a high-temperature Au(111), a selective debromination/coordination cascade reaction occurred, affording 2D organometallic coordination networks with phenyl-Au-isocyano nodes. By combining scanning tunneling microscopy and density functional theory calculations, we determined the structures of coordination products and the nature of coordination nodes, demonstrating a thermodynamically favorable pathway for forming the phenyl-Au-isocyano nodes.

Element-specific cluster growth on the two-dimensional metal–organic network

A porous two-dimensional metal–organic network (2D-MON) on a substrate captures deposited metal atoms and metal clusters growing in the pores of the 2D-MON. We found that the growth mechanisms of Ag, In, and Pd clusters in the 2D-MON synthesized from 1,3,5-tris(4-bromophenyl)benzene molecules on Ag(111) are different from each other, and the difference derives from the interaction of an adatom with the 2D-MON. Ag and Pd clusters grow from the 2D-MON since the interaction of Ag and Pd adatoms with the 2D-MON is attractive. In clusters grow inside of the pores of the 2D-MON since the interaction between an In adatom and the 2D-MON is repulsive. The growth process of metal clusters is determined by the element-specific behavior of metal adatoms in the pores, taking into account interactions with the 2D-MON.

Lanthanide-directed metal-organic coordination networks.

The synthesis of two-dimensional metal-organic networks (2D-MOCNs) on solid substrates is a rapidly growing field of research due to their potential applications in gas sensing, catalysis, energy storage, spintronics, and quantum information. In addition, the possibility of using lanthanides as coordination nodes makes them a very straightforward alternative to create an ordered array of magnetic atoms on a surface, thus paving the way for their use in information storage at the single-atom level. This feature article reviews the strategies to design two-dimensional periodic nanoarchitectures comprising lanthanide atoms in ultra-high vacuum (UHV) environment, focusing on lanthanide-directed 2D-MOCNs on metal surfaces and decoupling substrates. The characterization of their structure, electronic, and magnetic properties is also discussed, including the use of state-of-the-art scanning probe microscopies and photoelectron spectroscopies, complemented by density functional theory calculations and multiplet simulations.

Coordination-Driven Monolayer-to-Bilayer Transition in Two-Dimensional Metal-Organic Networks.

We report on monolayer-to-bilayer transitions in 2D metal-organic networks (MONs) from amphiphiles supported at the water-air interface. Functionalized calix[4]arenes are assembled through the coordination of selected transition metal ions to yield monomolecular 2D crystalline layers. In the presence of Ni(II) ions, interfacial self-assembly and coordination yields stable monolayers. Cu(II) promotes 2D coordination of a monolayer which is then diffusively reorganizing, nucleates, and grows a progressive amount of second layer islands. Atomic force microscopic data of these layers after transfer onto solid substrates reveal crystalline packing geometries with submolecular resolution as they are varying in function of the building blocks and the kinetics of the assembly. We assign this monolayer-to-bilayer transition to a diffusive reorganization of the initial monolayers owing to chemical vacancies of the predominant coordination motif formed by Cu2+ ions. Our results introduce a new dimension into the controlled monolayer-to-multilayer architecturing of 2D metal-organic networks.

Building two-dimensional metal-organic networks with tin.

We show that Sn atoms combined with organic ligands can be used to build 2D coordination networks on Au(111) surfaces.

Stabilizing and Organizing Bi3 Cu4 and Bi7 Cu12 Nanoclusters in Two-Dimensional Metal-Organic Networks.

Multinuclear heterometallic nanoclusters with controllable stoichiometry and structure are anticipated to possess promising catalytic, magnetic, and optical properties. Heterometallic nanoclusters with precise stoichiometry of Bi3 Cu4 and Bi7 Cu12 can be stabilized in the scaffold of two-dimensional metal-organic networks on a Cu(111) surface through on-surface metallosupramolecular self-assembly processes. The atomic structures of the nanoclusters were resolved using scanning tunneling microscopy and density functional theory calculations. The nanoclusters feature highly symmetric planar hexagonal shapes and core-shell charge modulation. The clusters are arranged as triangular lattices with a periodicity that can be tuned by choosing molecules of different size. This work shows that on-surface metallosupramolecular self-assembly creates unique possibilities for the design and synthesis of multinuclear heterometallic nanoclusters.

CO2 Binding and Induced Structural Collapse of a Surface-Supported Metal–Organic Network

Extensive efforts have been directed toward identifying catalytic material composites for efficiently transforming CO2 into valuable chemicals. Within this longstanding scientific challenge, the investigation of model systems is of particular interest to gain fundamental insight into the relevant processes and to synergistically advance materials functionalities. Inspired by the ubiquitous presence of metal–organic active sites in the conversion of CO2, we study here the interaction of CO2 with a two-dimensional metal–organic network synthesized directly on a metal surface as a model system for this class of compounds. The impact of individual CO2 molecules is analyzed using scanning tunneling microscopy supported by density functional theory calculations. Dosage of CO2 gas to the thermally robust Fe-carboxylate coordination structure at low temperatures (100 K) leads to a series of substantial rearrangements of the coordination motif, accompanied by a collapse of the entire network structure. Several bin...

Self-assembly of metal-organic coordination networks using on-surface synthesized ligands.

Supramolecular assembly and on-surface synthesis are two widely-used methods for constructing low-dimensional molecular nanostructures on surfaces. Here we describe an approach that combines both methods to create two-dimensional metal-organic networks with exceptionally large pores.

A two-dimensional metal organic network with 1,3,5-benzenetricarboxylate and cobalt (II) ions: synthesis, structure and topology

We herein report the synthesis and structure of a two dimensional (2D) metal-organic coordination polymer (or metal-organic network) which extends in two dimensions via Co2+ and 1,3,5-benzenetricarboxylate ions. The hydrothermal reaction of (2R,2′R,2″R)-2,2′,2″-(benzenetricarbonyltris(azanediyl))tripropanoic acid (parent ligand) with cobalt nitrate in the presence of pyridine lead to the decomposition of the parent ligand producing 1,3,5-benzenetricarboxylate, which in turn reacted with cobalt ions to afford a 2D network [Co1.5(BTC3–)·(pyridine)3·(H2O)](H2O)0.26·(MeOH) (1). This network was characterized by single crystal X-ray diffraction and IR spectroscopy. The topological study indicated that the framework is a 3,4-connected binodal net.

Poly[(μ2-3,6-di-4-pyridyl-1,2,4,5-tetrazine)(μ2-thiocyanato)copper(I)

The title compound, [Cu(NCS)(C12H8N6)]n, is a self-assembled two-dimensional metal–organic network. The Cu atom is linked by two N atoms from two 3,6-di-4-pyridyl-1,2,4,5-tetra­zine ligands and by the N and S atoms from two thio­cyanate ligands in a distorted tetra­hedral environment. The Cu atom and the thio­cyanate ligand occupy a crystallographic mirror plane m, and a crystallographic inversion centre is in the middle of the tetra­zine ring, generating the zigzag fashion of the two-dimensional network. The infinite –Cu—SCN—Cu—SCN– chain is due to translational symmetry along the a axis. These chains are further connected through the 3,6-di-4-pyridyl-1,2,4,5-tetra­zine ligands that bridge the CuI centers, generating a two-dimensional network. There are π—π stacking inter­actions between the pyridine and tetra­zine rings (perpendicular distances of 3.357 and 3.418 Å), with a centroid–centroid distance of 3.6785 (16) Å.

Two-dimensional metal–organic network with an unusual 36 topology and a cubic close packing pattern

X-Ray crystal structure of metal–organic network, [Zn3(SDA)3(DMF)2] (1) (H2SDA = trans-4,4′-stilbenedicarboxylic acid), composed of tri-nuclear secondary building units linked with SDA reveals a two-dimensional network with a relatively uncommon 36 topology and a cubic close packing mode.

Synthesis of two-dimensional metal–organic networks from 1,10-phenanthroline-chelated cadmium complex and polycarboxylate

The design of two 2D metal–organic frameworks using a 1,10-phenanthroline-chelated cadmium complex as precursor and a bridging polycarboxylate as linker is described. The reaction of Cd(NO 3) 2·4H 2O with the chelating ligand 1,10-phenanthroline (phen) at room temperature gave [Cd(phen)(NO 3) 2] ( 1) in high yield. Treatment of the inorganic precursor 1 with the polycarboxylate bridge ligand, benzene-1,4-dicarboxylic acid (H 2BDC) or benzene-1,2,4,5-tetracarboxylic acid (H 4btec), under mild hydrothermal conditions led to the formation of two metal–organic networks {[Cd(BDC)(phen)]·DMF} n ( 2) and [Cd 2(btec)(phen) 2] n ( 3). Single-crystal X-ray diffraction analyses showed that both products have two-dimensional sheet architectures. Compound 2 was constructed via the use of [Cd 2(O 2C ) 4] unit and BDC linker, whereas compound 3 involved the use of [CdO 4] core and btec bridge. The cadmium ions in compounds 2 and 3 are hepta- and hexa-coordinated, respectively. Thermogravimetric (TG) analyses showed that 2 and 3 are thermally stable ( T decomp. > 360 °C). Photoluminescence studies revealed that compounds 1– 3 displayed a strong fluorescent emission in the solid state at room temperature.