Leveraging Ligand Steric Demand to Control Ligand Exchange and Domain Composition in Stratified Metal-Organic Frameworks.

Incorporating diverse components into metal-organic frameworks (MOFs) can expand their scope of properties and applications. Stratified MOFs (sMOFs) consist of compositionally unique concentric domains (strata), offering unprecedented complexity through partitioning of structural and functional components. However, the labile nature of metal-ligand coordination handicaps achieving compositionally distinct domains due to ligand exchange reactions occurring concurrently with secondary strata growth.

Reversible solvent interactions with UiO-67 metal-organic frameworks.

The utility of UiO-67 Metal-Organic Frameworks (MOFs) for practical applications requires a comprehensive understanding of intermolecular host-guest MOF-analyte interactions. To investigate intermolecular interactions between UiO-67 MOFs and complex molecules, it is useful to evaluate the interactions with simple polar and non-polar analytes. This problem is approached by investigating the interactions of polar (acetone and isopropanol) and non-polar (n-heptane) molecules with functionalized UiO-67 MOFs via temperature programmed desorption mass spectrometry and temperature programmed Fourier transform infrared spectroscopy.

The diagnosis and treatment of central retinal artery occlusion with severe cardio-cerebrovascular disease: a case report.

Background: Central retinal artery occlusion (CRAO) is an acute eye disease that seriously damages vision. Patients with CRAO often have a combination of various cardio-cerebrovascular diseases (CCVDs), and CRAO patients often ignore their cardio-cerebrovascular disorders because of their ocular symptoms. In addition, there are few reports about CRAO patients with CCVDs received effective interventions implemented.

Simultaneously Enhanced Hydrophilicity and Stability of a Metal-Organic Framework via Post-Synthetic Modification for Water Vapor Sorption/Desorption.

With increasing demands for high-performance water sorption materials, metal-organic frameworks (MOFs) have gained considerable attention due to their high maximum uptake capacities. In many cases, however, high overall capacity is not necessarily accomplishing high working capacity under operating conditions, due to insufficient hydrophilicity and/or water stability. Herein, we present a post-synthetic modification (PSM) of MOF-808, with di-sulfonic acids enhancing simultaneously its hydrophilicity and water stability without sacrificing its uptake capacity of ≈30 mmol g .

Cholesterol affects the relationship between albumin and major adverse cardiac events in patients with coronary artery disease: a secondary analysis.

We aimed to examine whether the efficacy of the risk of poor prognosis in patients with coronary artery disease is jointly affected by total cholesterol and baseline serum albumin in a secondary analysis of previous study. We analyzed the data of 204 patients from October 2014 to October 2017 for newly diagnosed stable CAD. The outcome was major adverse cardiac events (MACE; defined as all cause mortality, non fatal myocardial infarction, and non fatal stroke).

Two-dimensional Zr/Hf-hydroxamate metal-organic frameworks.

Novel two-dimensional kagome metal-organic frameworks with mononuclear Zr/Hf nodes chelated by benzene-1,4-dihydroxamate linkers were synthesized. The MOFs, namely SUM-1, are chemically robust and kinetically favorable, as confirmed by theoretical and experimental studies. SUM-1(Zr) can be readily made into large (∼100 μm) single crystals and nanoplates (∼50 nm), constituting a versatile MOF platform.

Identifying UiO-67 Metal-Organic Framework Defects and Binding Sites through Ammonia Adsorption.

Ammonia is a widely used toxic industrial chemical that can cause severe respiratory ailments. Therefore, understanding and developing materials for its efficient capture and controlled release is necessary. One such class of materials is 3D porous metal-organic frameworks (MOFs) with exceptional surface areas and robust structures, ideal for gas storage/transport applications.

Rhamnolipid pretreatment enhances methane production from two-phase anaerobic digestion of waste activated sludge.

In this work, a rhamnolipid (RL) pretreatment technology was proposed to promote methane production from two-phase anaerobic digestion of waste activated sludge. In the first phase (i.e.

Tuning the Lewis acidity of metal-organic frameworks for enhanced catalysis.

The kinetics of hydrolysis of dimethyl nitrophenyl phosphate (DMNP), a simulant of the nerve agent Soman, was studied and revealed transition metal salts as catalysts. The relative rates of DMNP hydrolysis by zirconium and hafnium chlorides are in accordance with their Lewis acidity. In situ conversion of zirconium chloride to zirconium oxy-hydroxide was identified as the key step.

Atom-by-Atom Evolution of the Same Ligand-Protected Au, Au, AuCd, and Au Nanocluster Series.

Atom-by-atom manipulation on metal nanoclusters (NCs) has long been desired, as the resulting series of NCs can provide insightful understanding of how a single atom affects the structure and properties as well as the evolution with size. Here, we report crystallizations of Au(SAdm) and AuCd(SAdm) (SAdm = adamantanethiolate) which link up with Au(SAdm) and Au(SAdm) NCs and form an atom-by-atom evolving series protected by the same ligand. Structurally, Au(SAdm) has an Au(SAdm) surface motif which is longer than the Au(SAdm) on Au(SAdm), whereas AuCd(SAdm) lacks one staple Au atom compared to Au(SAdm) and thus the surface structure is reconstructed.

Heteroatom Tracing Reveals the 30-Atom Au-Ag Bimetallic Nanocluster as a Dimeric Structure.

Understanding the formation of face-centered cubic (fcc) nanostructures at the atomic level remains a major task. With atomically precise nanoclusters (NCs) as model systems, herein we devised an atom-tracing strategy by heteroatom doping into Au(SR) (SR = S-CH) to label the specific positions in M(SR) NCs (M = Au/Ag), which clearly reveals the dimeric nature of M. Interestingly, the specific position is also consistent with the Ag-doping site in M(SR).

Ship-in-a-Bottle Preparation of Long Wavelength Molecular Antennae in Lanthanide Metal-Organic Frameworks for Biological Imaging.

While metal-organic frameworks (MOFs) have been identified as promising materials for sensitizing near-infrared emitting lanthanide ions (Ln) for biological imaging, long-wavelength excitation of such materials requires large, highly delocalized organic linkers or guest-chromophores. Incorporation of such species generally coincides with fewer Ln emitters per unit volume. Herein, the excitation bands of ytterbium-based MOFs are extended to 800 nm via the postsynthetic coupling of acetylene units to form a high density of conjugated π-systems throughout MOF pores.

Luminescence "Turn-On" Detection of Gossypol Using Ln-Based Metal-Organic Frameworks and Ln Salts.

Gossypol (Gsp), a natural toxin concentrated in cottonseeds, poses great risks to the safe consumption of cottonseed products, which are used extensively throughout the food industry. In this work, we report the first luminescence "turn-on" sensors for Gsp using near-infrared emitting lanthanide (Ln) materials, including Ln MOFs and Ln salts. We first demonstrate that the Yb photoluminescence of a Yb MOF, Yb-NH-TPDC, can be employed to selectively detect Gsp with a limit of detection of 25 μg/mL via a "turn-on" response from a completely nonemissive state in the absence of Gsp.

Au Ag Nanoclusters with Non-Metallicity: A Drum of Silver-Rich Sites Enclosed in a Marks-Decahedral Cage of Gold-Rich Sites.

The synthesis and structure of atomically precise Au Ag (average x=98) alloy nanoclusters protected by 55 ligands of 4-tert-butylbenzenethiolate are reported. This large alloy structure has a decahedral M (M=Au/Ag) core. The Au atoms are localized in the truncated Marks decahedron.

One Approach for Two: Toward the Creation of Near-Infrared Imaging Agents and Rapid Screening of Lanthanide(III) Ion Sensitizers Using Polystyrene Nanobeads.

The unique luminescence properties of lanthanide(III) ions (Ln) in the near-infrared (NIR) range are attracting major attention in view of their exciting applications in the fields of technology, telecommunications, biology, and medicine. One of the main strategies to design luminescent Ln-based compounds relies on their sensitization through appropriate chromophoric ligands. The choice of the chromophores depends on the nature of Ln and, as of today, still partially requires experimental trials, in particular, for the creation of luminescent compounds incorporating NIR-emitting Ln.

Growth of ZIF-8 on molecularly ordered 2-methylimidazole/single-walled carbon nanotubes to form highly porous, electrically conductive composites.

The combination of porosity and electrical conductivity in a single nanomaterial is important for a variety of applications. In this work, we demonstrate the growth of ZIF-8 on the surface of single-walled carbon nanotubes (SWCNTs). The growth mechanism was investigated and a molecularly ordered imidazole solvation layer was found to disperse SWCNTs and promote crystal growth on the sidewalls.

Multivariate Stratified Metal-Organic Frameworks: Diversification Using Domain Building Blocks.

We introduce the concept of domain building blocks (DBBs) as an effective approach to increasing the diversity and complexity of metal-organic frameworks (MOFs). DBBs are defined as distinct structural or compositional regions within a MOF material. Using the DBB approach, we illustrate how an immense number of multivariate MOF materials can be prepared from a small collection of molecular building blocks comprising the distinct domains.

Near infrared excitation and emission in rare earth MOFs encapsulation of organic dyes.

We successfully demonstrate that metal-organic frameworks (MOFs) can be designed to be excited and emit within the biological diagnostic window (650-1450 nm). An isoreticular series of anionic rare earth MOFs with topology was synthesized using 10 different rare earth elements (Y, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) and common linear ditopic ligands. Five different cationic dye molecules were incorporated into the MOFs ion exchange.

A Correlated Series of Au/Ag Nanoclusters Revealing the Evolutionary Patterns of Asymmetric Ag Doping.

Doping of metal nanoclusters is an effective strategy for tailoring their functionalities for specific applications. To gain fundamental insight into the doping mechanism, it is of critical importance to have access to a series of correlated bimetal nanoclusters with different doping levels and further reveal the successive transformations. Herein, we report asymmetric doping of Ag into an Au nanocluster to form a series of new Au/Ag bimetal nanoclusters and the effects of doping on the evolution of size, structure, and properties based upon X-ray crystallography and optical spectroscopy analyses.

Modulating the hierarchical fibrous assembly of Au nanoparticles with atomic precision.

The ability to modulate nanoparticle (NP) assemblies with atomic precision is still lacking, which hinders us from creating hierarchical NP organizations with desired properties. In this work, a hierarchical fibrous (1D to 3D) assembly of Au NPs (21-gold atom, Au) is realized and further modulated with atomic precision via site-specific tailoring of the surface hook (composed of four phenyl-containing ligands with a counteranion). Interestingly, tailoring of the associated counterion significantly changes the electrical transport properties of the NP-assembled solids by two orders of magnitude due to the altered configuration of the interacting π-π pairs of the surface hooks.

Single-ligand exchange on an Au-Cu bimetal nanocluster and mechanism.

An Au-Cu bimetallic nanocluster co-capped by selenolate and phosphine is obtained and its X-ray structure shows an icosahedral Au13 kernel surrounded by three CuSe2PPh2Py motifs and one CuSe3 motif, formulated as [Au13Cu4(PPh2Py)3(SePh)9]. Interestingly, a single-ligand exchange process is observed in the growth reaction, in which an [Au13Cu4(PPh2Py)4(SePh)8]+ intermediate is first formed, but a prolonged reaction leads to one PPh2Py ligand being selectively replaced by a PhSe-ligand. DFT simulations reveal that both steric hindrance and bond dissociation energy have great effects on the single-ligand exchange reaction as well as the thermodynamics, which help to understand the mechanism of the ligand exchange.

Programmable Topology in New Families of Heterobimetallic Metal-Organic Frameworks.

Using diverse building blocks, such as different heterometallic clusters, in metal-organic framework (MOF) syntheses greatly increases MOF complexity and leads to emergent synergistic properties. However, applying reticular chemistry to syntheses involving more than two molecular building blocks is challenging and there is limited progress in this area. We are therefore motivated to develop a strategy for achieving systematic and differential control over the coordination of multiple metals in MOFs.

Reconstructing the Surface of Gold Nanoclusters by Cadmium Doping.

Atomically precise metal nanoclusters with tailored surface structures are important for both fundamental studies and practical applications. The development of new methods for tailoring the surface structure in a controllable manner has long been sought. In this work, we report surface reconstruction induced by cadmium doping into the [Au(SR)] (R = cyclohexyl) nanocluster, in which two neighboring surface Au atomic sites "coalesce" into one Cd atomic site and, accordingly, a new bimetal nanocluster, [AuCd(SR)], is produced.

Shuttling single metal atom into and out of a metal nanoparticle.

It has long been a challenge to dope metal nanoparticles with a specific number of heterometal atoms at specific positions. This becomes even more challenging if the heterometal belongs to the same group as the host metal because of the high tendency of forming a distribution of alloy nanoparticles with different numbers of dopants due to the similarities of metals in outmost electron configuration. Herein we report a new strategy for shuttling a single Ag or Cu atom into a centrally hollow, rod-shaped Au nanoparticle, forming AgAu and CuAu nanoparticles in a highly controllable manner.

Tailoring the Structure of 58-Electron Gold Nanoclusters: AuS(S-Nap) and Its Implications.

We report the synthesis and crystal structure determination of a gold nanocluster with 103 gold atoms protected by 2 sulfidos and 41 thiolates (i.e., 2-naphthalenethiolates, S-Nap), denoted as AuS(S-Nap).