Metal Organic Layers Research Articles

Ni-MOL/In2Se3 heterostructure construction with mixed metal (Ti/Ni) for efficient photocatalytic tetracycline degradation

To investigate the mechanism of bimetallic 2-dimension (2D) catalyst existing in the current photocatalytic degradation process, the tetracycline (TC) degradation performance and mechanism by bimetallic 2D photocatalyst was studied extensively. Nickel metal-organic layer (Ni-MOL) and In2Se3, a typical 2D semiconductor photocatalyst, shows great potential for photocatalytic degradation of TC. Herein, an In2Se3 assisted Ni-MOL composite bimetallic photocatalyst was assembled, of which could obtain the degradation rate of 96.4% within 90 min for TC under visible light. Ni-MOL was the main active site for TC degradation by photo-induced holes which located at the Ni atom active site during the photocatalytic process. The role of In2Se3 and the element of Ti in Ni-MOL was to assist Ni-MOL by providing more photo-induced carriers and inhibiting carrier recombination. This work makes a contribution to the application of 2D bimetallic photocatalytic in TC degradation.

Environmentally persistent free radicals in bismuth-based metal–organic layers derivatives: Photodegradation of pollutants and mechanism unravelling

Formation of environmentally persistent free radicals (EPFRs) on carbonaceous material has aroused increasing research attentions. In terms of metal organic frameworks (MOFs) derivatives, however, scarce studies have dedicated to the relevant aspects. Herein, EPFRs have been detected in Bi-metal organic layers (Bi-MOLs) derivatives. The corresponding g-factors and concentrations of EPFRs on Bi2O3@C by pyrolyzed at different temperatures were 2.0041–2.0046 and 7.04 × 1019-1.77 × 1020 spins/g, respectively. Interestingly, similar EPFRs signals were also monitored in HKUST-1 based and UiO-66 based derivatives. We observed that Bi2O3@C system with the highest EPFRs concentration exhibited superior degradation and mineralization efficiency for phenol and tetracycline. Its excellent photocatalytic performance was mainly attributed to the interaction between the internal EPFRs and photoinduced active species, which promoted more generation of reactive oxygen species (ROS) radicals. This hypothesis was supported by line correlations for EPFRs concentration vs. degradation kinetics in samples pyrolyzed at different temperatures (R2 = 0.946). Most significantly, mechanism investigation combined with DFT calculation indicated that the EPFRs not only promote the generation of 1O2 and •OH via molecular oxygen activation pathway but also provided a possibility of enhancing water oxidation by holes. These findings pave the way for MOFs derivative's implication and insight into the role of EPFRs in photocatalysis.

Bifunctional Metal-Organic Layers for Tandem Catalytic Transformations Using Molecular Oxygen and Carbon Dioxide.

Tandem catalytic reactions improve atom- and step-economy over traditional synthesis but are limited by the incompatibility of the required catalysts. Herein, we report the design of bifunctional metal-organic layers (MOLs), HfOTf-Fe and HfOTf-Mn, consisting of triflate (OTf)-capped Hf6 secondary building units (SBUs) as strong Lewis acidic centers and metalated TPY ligands as metal active sites for tandem catalytic transformations using O2 and CO2 as coreactants. HfOTf-Fe effectively transforms hydrocarbons into cyanohydrins via tandem oxidation with O2 and silylcyanation whereas HfOTf-Mn converts styrenes into styrene carbonates via tandem epoxidation and CO2 insertion. Density functional theory calculations revealed the involvement of a high-spin FeIV (S = 2) center in the challenging oxidation of the sp3 C-H bond. This work highlights the potential of MOLs as a tunable platform to incorporate multiple catalysts for tandem transformations.

Nanoscale Metal–Organic Layers for Biomedical Applications

ConspectusAs a monolayer version of nanoscale metal organic frameworks (nMOFs), nanoscale metal–organic layers (nMOLs) have recently emerged as a novel class of two-dimensional (2D) molecular nanomaterials. nMOLs are built from metal-oxo secondary building units (SBUs) with suitable coordination modes and organic linkers with proper geometries in a bottom-up fashion by carefully controlling the reaction temperature, capping agents, water concentration, and other parameters. M6-BTB and related nMOLs are formed by linking M6(μ3-O)4(μ3-OH)4 (M = Zr4+, Hf4+, Ce4+) SBUs and planar tricarboxylate bridging ligands such as 1,3,5-benzene-tribenzoate (BTB), while M12-nMOLs are constructed from M12(μ3-O)8(μ3-OH)8 (μ2-OH)6 (M = Zr4+, Hf4+) SBUs and linear dicarboxylate ligands such as 5,15-di(p-benzoato)porphyrin (DBP). Mechanistic studies revealed the important roles of capping agents and water on the growth of nMOLs and the stepwise growth process involving the partial hydrolysis of metal ions to form metal-oxo clusters with capping agents and the subsequent replacement of capping agents by bridging ligands. The 2D nature of nMOLs facilitates the postsynthetic modification of bridging ligands and the exchange of capping agents to simultaneously incorporate multifunctionalities into nMOLs.In this Account, we discuss the design principles, growth mechanisms, and postsynthetic functionalization strategies for nMOLs and summarize our research efforts to design nMOLs for various biological and biomedical applications. We first outline the strategies for the design and synthesis of M6- and M12-nMOLs via a dimensional reduction strategy and discuss the growth mechanisms of nMOLs. We then highlight the methods for the postsynthetic functionalization of nMOLs. We demonstrate the application of nMOLs in two broad categories. We first show the design and development of nMOLs for radiotherapy–radiodynamic therapy (RT–RDT) and further combination with checkpoint blockade immunotherapy. The evolution of Hf6-nMOLs to Hf12-nMOLs illustrates the control of nMOL morphology and photosensitizer loading for optimal RT–RDT effects. The nMOL-mediated RT–RDT is further combined with checkpoint blockade cancer immunotherapy to enable the treatment of systemic diseases via local X-ray irradiation. We next demonstrate nMOLs as a versatile platform for ratiometric sensing/imaging and drug delivery. The easily accessible sites on SBUs and ligands in nMOLs provide conjugation sites for multifunctional sensors and drugs, allowing for simultaneous ratiometric sensing of the pH and oxygen concentration or pH and glutathione concentration in mitochondria as well as highly effective photodynamic therapy with insoluble conjugated zinc phthalocyanine.We discuss the limitations of currently available nMOLs in terms of a lack of structural diversity and lower stability compared to nMOFs. We also point out the untapped potential of using the inherent hierarchy of SBU and bridging ligand structures to integrate multiple functionalities for synergistic functions. With the establishment of general design principles and an understanding of nMOL growth mechanisms, we believe that nMOLs will emerge as a fertile research field with great potential for applications beyond radiotherapy–radiodynamic therapy, immunotherapy, multifunctional biosensing, and drug delivery.

Effects of two different solvents on Schottky barrier of organic device

In this paper, the effects of two different solvents on the Schottky barrier of ITO/ blend of methyl red dye—fullerene nanoparticles/Al - M electrode have been studied. We have taken chlorobenzene solvent and toluene solvent. Three different devices have been made by taking three different weight ratios of the dye—nanoparticles blend which is 1:1, 1:2, and 2:1. The estimation of the interfacial Schottky barrier at the junction of metal-organic dye is estimated using the device’s dark I—V plot. Interfacial Schottky barrier at the metal-organic junction is least for 2:1 weight ratio of dye - nanoparticle blend in chlorobenzene solvent but for toluene solvent, the Schottky barrier is least for 1:2 weight ratio of dye—nanoparticle blend. The lowering of barrier height at 2:1 and 1:2 ratios in Schottky barrier contacts prepared with chlorobenzene and toluene solvents can be attributed to the filling up of traps at the metal-organic layer interface. The Norde method is also used to check the consistency of the obtained value of the Schottky barrier measured from I—V plots. Reduction in Schottky barrier results in improved current injection process at the metal-organic interface.

Effect of Single Walled Carbon Nanotubes on the Series Resistance and Trap Energy of Malachite Green Dye Based Organic Device

In this paper, we have estimated the series resistance (Rs) and the trap energy (Ec) of the sandwiched type Malachite Green (MG) dye-based organic device and have also observed the influence of single-walled carbon nanotubes (SWCNT) on both of these parameters. To form the organic device, we have used Indium Tin Oxide (ITO) coated glass as the front electrode and Aluminium (Al) as a back electrode by using the spin coating technique. The values of series resistance are measured from both I-V characteristics and by utilizing Cheung Function due to the non ideal behavior of organic devices. We have also extracted the values of Rsby using H (I) versus I plot and verified the values with the measured values of Rsfrom the Cheung function. The extracted values of series resistance using these three processes remain consistent with each other in showing that the values of series resistance have been reduced considerably in the presence of SWCNT. The trap energy has been estimated from the steady-state current-voltage characteristics. There is a significant correlation in between series resistance and the trap energy of the organic device. The presence of Single-Walled Carbon Nanotubes reduces the trap energy from 0.086 eV to 0.057 eV. Lowering of the trap energy of the metal-organic layer interface in presence of Single Walled Carbon Nanotubes attributes to the reduction of the value of the series resistance. The extracted value of Rsdecreases from 0.154 MΩ to 0.0389 MΩ in presence of SWCNT. Decrease in the value of both of these parameters in the presence of SWCNT will definitely improve the charge transport mechanism of the organic device and thereby the conductivity.

Facile Synthesis of Metal-Organic Layers with High Catalytic Performance toward Detoxification of a Chemical Warfare Agent Simulant.

Two-dimensional (2D) metal-organic layer (MOL) materials are highly desired against chemical warfare agents (CWAs). However, the rapid synthesis of 2DMOLs with open metal sites in a single step is very challenging. Herein, a facile bottom-up method for synthesizing MOLs with microwave assistance is applied to produce Zr/Hf-BTB MOLs, composed of six-connected M6O4(OH)412+ and the tritopic carboxylate ligand 1,3,5-tris(4-carboxyphenyl)benzene (BTB). The synthesis and ligand exchange steps can be combined into a single step to yield MOLs with active open sites directly. The as-synthesized MOLs demonstrate excellent catalytic performance toward the degradation of a CWA simulant. The theoretical calculations confirm that the high catalytic activity is due to the formate groups coordinated to the metal nodes being replaced by hydroxyl groups. The present work not only develops a method for the fast synthesis of 2D MOLs with active open metal sites in a single step but also provides a first demonstration for the application of 2D metal coordination materials in CWA protection.

From 3D to 2D: Multifunctional metal-organic layers for organic synthesis

Recently, in <i>Journal of the American Chemical Society</i>, Quan et al. presented a novel bifunctional metal-organic layer (MOL) that hierarchically integrated organic photosensitizer eosin Y and 2,2′:6′,2″-terpyridine ligated iron triflate. Under blue light irradiation, the self-supporting two-dimensional MOL efficiently catalyzed trifluoromethylative difunctionalization of alkenes, including bulky bioactive molecules. This work highlights the bright future of low-dimensional molecular materials in organic synthesis.

Model Study of Penetration of Cl− Ions from Solution into Organic Self-Assembled-Monolayer on Metal Substrate: Trends and Modeling Aspects

Organic molecules that form self-assembled-monolayers on metal substrates may provide efficient corrosion protection. Herein we study how such self-assembled-monolayers hinder the penetration of ions from aqueous solution toward the metal substrate. We first elucidate some aspects that are relevant for modeling charged ions near surfaces with slab models that utilize periodic-boundary-conditions, in particular: (i) solvation effects, (ii) inter-ion electrostatics, (iii) depolarization effects, and (iv) effects of periodic-boundary-conditions along lateral directions and, for multi-slab models, also along the surface normal direction. The last two effects are artifacts hence they can be avoided or at least minimized by proper modeling. We further present a simple scheme that describes the activation barrier for penetration into self-assembled-monolayer as a function of the electrode potential and show that the activation barrier decreases as the electrode potential increases, as would be intuitively expected, however, for thick self-assembled-monolayers the barrier remains sizable even at rather positive potentials, which may be one of the reasons why dense and sufficiently thick self-assembled-monolayers can efficiently inhibit corrosion. By utilizing a simple model where metal substrate, organic layer, and aqueous solvent are described implicitly by dielectric continuum slabs, we analyze two important effects by which self-assembled-monolayers hinder the penetration of ions toward the metal substrate. The first effect is due to inferior solvation of ions in organic layer compared to that in aqueous solvent and the estimated difference is larger than 1 eV. This effect is independent of the thickness of the organic layer, provided that the layer is sufficiently thick (≳10 Å). The second effect is due to electric field at the electrochemical interface and the extent by which it affects the penetration of depends on the electrode potential and on the thickness of the organic layer. Other effects, such as local deformation of organic layer during penetration, cannot be described by current simple models and will be considered in our next publication. Finally, calculations indicate that due to stronger solvation of Na+ counter-ions their penetration into organic layer is inferior to that of . Energetically the most favorable way for Na+ to penetrate is in the form of Na+/ ion-pairs, but it is inferior to penetration of alone.

Magnetic porous carbon nanocomposite derived from cobalt based-metal-organic framework for extraction and determination of homo and hetero-polycyclic aromatic hydrocarbons

Herein, a novel magnetic porous carbon nanocomposite derived from a cobalt based-metal-organic framework was synthesized and evaluated for simultaneous preconcentration of homo and hetero-polycyclic aromatic hydrocarbons. Briefly, magnetite nanoparticles (MNPs) were synthesized and then were coated with a metal-organic framework layer. Finally, the magnetic nanocomposite was carbonized under an inert atmosphere to obtain the magnetic porous carbon (MPC). Various characterization techniques such as FT-IR spectroscopy, transmission and scanning electron microcopies, vibrating sample magnetometry, and X-ray diffraction were employed. Applicability of the MPC was explored using benzothiophene, dibenzothiophene, 9,10-dimethylanthracene, and benz[α]anthracene as the model analytes. Limits of detection and linearities were achieved in the range of 0.06–0.18 μg L−1 and 0.25–500 μg L−1, respectively. Precision of the method as RSDs was evaluated which was in the range of 4.2–7.0% (within-day, n = 5) and 8.2–11.3% (between-day, n = 3). Ultimately, the method was applied to analyze two seawater samples and satisfactory results (RSDs%, 5.0–9.0%; relative recoveries, 89–104%) were obtained.

Light-Driven Proton Transport Across Liposomal Membranes Enabled by Janus Metal-Organic Layers

Photo-generation of a proton gradient over a lipid bilayer is of interest due to its essential role in photosynthetic bacteria. Membrane asymmetry is key to the generation of a proton gradient via directional proton transport. Here we report a light-driven proton pump based on two-dimensional, porphyrin-based Janus metal-organic layers (Janus-MOLs) embedded in liposomes. We developed a microemulsion-based method to functionalize the Janus-MOLs with carboxyquinone on one side and Acitretin on the other side. By attaching the Janus-MOLs to liposome surfaces, we obtained a mimic to photosynthetic bacteria. Upon photoexcitation, the porphyrins initiate electron and hole transfers to carboxyquinone and Acitretin, respectively, which undergo redox reactions with freely diffusing quinone (Q) / hydrosemiquinone (HQ·) in the lipid bilayer to produce a concentration gradient of quinone-based species. Owing to different pKa values of HQ+ and HQ ·, these redox reactions trigger proton transport across the membrane to create a pH gradient, which drives ATP production by CF0F1-ATP synthase in a similar fashion as photosynthetic bacteria.

Electronic structure modulation with ultrafine Fe3O4 nanoparticles on 2D Ni-based metal-organic framework layers for enhanced oxygen evolution reaction

Two-dimensional (2D) metal organic frameworks (MOFs) are emerging as low-cost oxygen evolution reaction (OER) electrocatalysts, however, suffering aggregation and poor operation stability. Herein, ultrafine Fe3O4 nanoparticles (diameter: 6 ± 2 nm) are homogeneously immobilized on 2D Ni based MOFs (Ni-BDC, thickness: 5 ± 1 nm) to improve the OER stability. Electronic structure modulation for enhanced catalytic activity is studied via adjusting the amount of Fe3O4 nanoparticles on Ni-BDC. The optimal Fe3O4/Ni-BDC achieves the best OER performance with an overpotential of 295 mV at 10 mA cm−2, a Tafel slope of 47.8 mV dec-1 and a considerable catalytic durability of more than 40 h (less than 5 h for Ni-BDC alone). DFT calculations confirm that the active sites for Fe3O4/Ni-BDC are mainly contributed by Fe species with a higher oxidation state, and the potential-determining step (PDS) is the formation of the adsorbed O* species, which are facilitated in the composite.

Two-Dimensional Single-Atom Catalyst TM3(HAB)2 Monolayers for Electrocatalytic Dinitrogen Reduction Using Hierarchical High-Throughput Screening.

As an environmentally friendly and sustainable strategy to produce ammonia, the electrocatalytic nitrogen reduction reaction (eNRR) is facing the challenge of low conversion rates and high overpotential, to solve which efficient catalysts are urgently needed. Here, a new class of two-dimensional metal-organic layers (MOLs) TM3(HAB)2 (TM = 30 transition metals; HAB = hexaaminobenzene) were evaluated via a three-step high-throughput screening combined with the spin-polarized density functional theory (DFT) method to obtain eligible TM3(HAB)2 catalysts embedded with transition metal atoms from 3d to 5d. Our investigation revealed that Nb3(HAB)2, Mo3(HAB)2, and Tc3(HAB)2 are eligible NRR candidates, among which Tc3(HAB)2 possesses the best catalytic performance with a lowest onset potential of -0.63 V via both distal and alternating pathways and an ultralow NH3 desorption free energy of 0.22 eV. Furthermore, the band structures of three catalysts show their nice conductivity. The corresponding projected density of states (PDOS) illustrate that high catalytic activity can be ascribed to apparent orbital hybridization and charge transfer between catalysts and adsorbed N2. Later, stability and selectivity of all three candidates were computed, Tc3(HAB)2 and Nb3(HAB)2 catalysts are proved to facilitate dinitrogen reduction and exhibit good stability and high selectivity, yet NRR on the Mo3(HAB)2 catalyst is inhibited by hydrogen evolution reaction (HER). Based on the abovementioned studies, we concluded that Tc3(HAB)2 and Nb3(HAB)2 monolayers are promising catalysts for nitrogen fixation. We expect this work to fill the gap of exploring more eligible single-atom catalysts (SACs) anchored with transition metal atoms on MOLs for NRR.

Robust photocatalytic hydrogen production on metal-organic layers of Al-TCPP with ultrahigh turnover numbers

The development of robust photocatalytic systems is key to harvest the solar power for hydrogen production. In the current study, a series of aluminum-based porphyrinic metal organic frameworks (Al-TCPP) with various morphologies of bulk, carambola-like and nanosheets are synthesized with modulated layer thickness. Morphology-dependent photocatalytic activities in hydrogen production are witnessed and inversely correlate to the thickness of the Al-TCPP micro-platelets or nanosheets. Particularly, the exfoliated metal organic layers (MOLs) of Al-TCPP demonstrated a high hydrogen yield rate of 1.32 × 104 µmol h−1 g−1 that is 21-fold of that from the bulk catalyst, as well as an exceptional TON of 6704 that seldom seen in literature. Through comprehensive photochemical characterizations, the remarkable photocatalytic performance of Al-TCPP-MOL is attributed to the great charge separation efficiency and transfer kinetics endowed by the ultrathin 2D morphology with extended active surface area.

Photocatalytic Functionalization of Alkenes with a Metal–Organic Layer Containing Eosin Y and Iron

Photocatalytic Functionalization of Alkenes with a Metal–Organic Layer Containing Eosin Y and Iron

Chemically Exfoliated Semiconducting Bimetallic Porphyrinylphosphonate Metal–Organic Layers for Photocatalytic CO2 Reduction under Visible Light

In this paper, we report the first example of semiconducting porphyrinylphosphonate metal–organic framework (MOF) [Co(Ni-H7TPPP)2]·8H2O and its chemical exfoliation into ultrathin metal–organic lay...

Hydrophilic and hydrophobic calcium-phosphonate monoester metal-organic layers

Two isostructural calcium-phosphonate monoester layered coordination polymers grafted with methoxyethyl (Ca-L1) and ethyl (Ca-L2) groups were synthesized by solvothermal method. Both materials can be exfoliated into metal–organic layers (MOLs) with structure retention via a “top-down” approach. The introduction of phosphonate monoester (PME) grafting groups not only ensures the formation of two-dimensional layers but also plays an important role to regulate the hydrophilicity-hydrophobicity and water stability of the materials.

Study on the effect of singlewalled carbon nanotubes on junction properties of Safranin –T dye-based organic device

In this work, junction properties of metal-organic dye contact have been studied and alteration of these properties in presence of single walled carbon nanotubes has been observed. Junction properties of metal-organic interface significantly influence the device performance. Present work studies barrier potential and trap energy under the influence of single walled carbon nanotubes. Barrier inhomogeneity and the effect of image charge on lowering of barrier potential have also been studied. Formation of the organic device has been done by sandwiching Safranin - T dye in between two electrodes which are Indium Tin Oxide coated glass substrate and Aluminium respectively. Charge flow at the metal–organic layer interface has been analyzed by Richardson –Schottky thermionic emission theory. Both barrier potential and trap energy have been estimated from the steady-state current-voltage characteristics of the device. The incorporation of single walled carbon nanotubes lowers both of these parameters results in improvement of current flow at the metal-organic contact.

Design of [formula omitted]-conjugated flexible semiconductive 2D MOF and MOF derived CuO nano-spheres for solvent free C-X (S, O) hetero-coupling catalysis with enhanced conductivity

A flexible, 2-fold interpenetrated 3D supramolecular structure [Cu(ndc2−)(1,10-phen)]n (where ndc2−=2,6-napthalenedicarboxylate and 1,10-phen = 1,10-phenanthroline) comprising neutral 2D metal–organic layers as the basic building block was prepared. Structural study reveals that metal ions are bridged by ndc2− ligands to form 2D coordination layers and the coordinated 1,10-phen moieties are hanging from the layers in the interlamellar spaces. The gliding motion of π⋯π stacked layers through 1,10-phen moieties was found to be responsible for the flexibility of MOF and the consequent extended conjugation also rendered semiconducting behaviour in the material. Thermal stability studies revealed that the framework was pretty stable below 260°C. Additionally, the MOF was characterized by performing BET adsorption and photoluminescence studies. Further, the MOF was calcinated at 650°C to prepare well defined, nearly uniform and spherical shaped CuO nanoparticles (CuO-NPs) with an average size of ∼25 nm. Interestingly, CuO-NPs showed around 16 times more conductivity (4.8 × 10−2 S/cm) in relative to the parent MOF (3 x 10−3 S/cm). CuO-NPs induced cross-coupling reactions of alcohols and thiols with arylhalides have been reported. A simple, general, ligand-free and solvent-free procedure for the efficient synthesis of the cross-coupled products in high yield was successfully demonstrated.

Bifunctional Metal-Organic Layer with Organic Dyes and Iron Centers for Synergistic Photoredox Catalysis.

Here we report the design of a bifunctional metal-organic layer (MOL), Hf-EY-Fe, by bridging eosin Y (EY)-capped Hf6 secondary building units (SBUs) with Fe-TPY (TPY = 4'-(4-carboxyphenyl)[2,2':6',2''-terpyridine]-5,5''-dicarboxylate) ligands. With the organic dye EY as an efficient photosensitizer and TPY-Fe(OTf)2 as the catalytic center, Hf-EY-Fe efficiently catalyzes aminotrifluoromethylation, hydroxytrifluoromethylation, and chlorotrifluoromethylation of alkenes. Hf-EY-Fe also catalyzes the synthesis of CF3-substituted derivatives of large bioactive molecules such as rotenone, estrone, and adapalene with sizes of up to 2.2 nm. The proximity between EY and iron centers and their site isolation in Hf-EY-Fe enhance catalytic activity while inhibiting their mutual deactivation, leading to high turnover numbers of up to 1840 and good recyclability of the MOL catalyst.