Synthesis and investigation of the thermal proper- ties of [Co(N H-3)(6)] [Co(C2O4)(3)]center dot 3H(2)O and [Ir(NH3)(6)][Ir(C2O4)(3)]

The complexes [Co (NH3)(6)][Ir (C2O4)(3)] and [Ir(NH3)(6)][Co (C2O4)(3)center dot H2O have previously been synthesized and their thermal properties studied. The [Ir(NH3)(6)][Ir(C2O4)(3)] and [Co(NH3)(6)][Co(C2O4)(3)]center dot 3H(2)O complexes considered here are the end members in a series of possible isostructural solid solutions based on the complex salts in the Co-Ir system. Their crystal structures and thermal properties are described in detail, including temperature-dependent in situ X-ray diffraction. During the thermolysis of these compounds, layered metal nanoparticles are formed. Close attention is paid to the details of the [Co(NH3)(6)][Ir(C2O4)(3)] synthesis. It has been shown that the formation of this complex salt is temperature dependent; upon heating, a new phase of the K-3[Co(NH3)(6)][Ir(C2O4)(3)](2)center dot 6H(2)O salt is formed, which incorporates the initial iridium compound into the crystal structure of the double complex salt. The target [Co(NH3)(6)][Ir(C2O4)(3)] product is obtained if the synthesis is carried out at room temperature

Post-synthetic Covalent Grafting of Amines to NH2-MOF for Post-Combustion Carbon Capture

Herein, we report a post-synthetic modification strategy to covalently graft polyamines, including ethylenediamine (ED), diethylenetriamine (DETA), tris(2-aminoethyl)amine (TAEA), and polyethyleneimine (PEI) to the amino-ligand of a Cr-MOF, NH2-Cr-BDC, for post-combustion carbon capture applications. X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) reveal that ~45% of the MOF ligands are grafted with polyamines. Also, after assessment of CO2 uptake, CO2/N2 selectivity, isosteric heats of CO2 adsorption, separation performance during humid CO2/N2 (15/85) breakthrough experiments, and cyclability, the study reveals an enhanced performance for the polyamine composites and the following performance trend: NH2-Cr-BDC<ED<DETA<TAEA<PEI. The best-performing materials, including TAEA and PEI-grafted MOFs, offer CO2 uptakes of 1.0 and 1.55 mmol/g, respectively, at 0.15 bar and 313 K. Further, these composites also offer a high CO2 capacity after 200 temperature swing adsorption/desorption (TSA) cycles in simulated humid flue gas. Last, after soaking the composites in water, we show that there is no loss of CO2 capacity; on the contrary, when the same MOF is impregnated with polyamines using traditional approaches, there is ~85 % CO2 capacity loss after soaking. Thus, this covalent grafting strategy successfully immobilizes amines in MOF pores preventing leaching and hence could be an effective strategy to extend adsorbent lifetime

Understanding How Ligand Functionalization Influences CO 2 and N 2 Adsorption in a Sodalite Metal–Organic Framework

International audienc

3D vs. turbostratic: controlling metal-organic framework dimensionality via N-heterocyclic carbene chemistry.

Using azolium-based ligands for the construction of metal-organic frameworks (MOFs) is a viable strategy to immobilize catalytically active N-heterocyclic carbenes (NHC) or NHC-derived species inside MOF pores. Thus, in the present work, a novel copper MOF referred to as Cu-Sp5-BF4, is constructed using an imidazolinium ligand, H2Sp5-BF4, 1,3-bis(4-carboxyphenyl)-4,5-dihydro-1H-imidazole-3-ium tetrafluoroborate. The resulting framework, which offers large pore apertures, enables the post-synthetic modification of the C2 carbon on the ligand backbone with methoxide units. A combination of X-ray diffraction (XRD), solid-state nuclear magnetic resonance (ssNMR) and electron microscopy (EM), are used to show that the post-synthetic methoxide modification alters the dimensionality of the material, forming a turbostratic phase, an event that further improves the accessibility of the NHC sites promoting a second modification step that is carried out via grafting iridium to the NHC. A combination of X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) methods are used to shed light on the iridium speciation, and the catalytic activity of the Ir-NHC containing MOF is demonstrated using a model reaction, stilbene hydrogenation

Enhancing MOF performance through the introduction of polymer guests

In this contribution, recent advances in the construction of MOF-polymer composites and their corresponding applications are briefly reviewed. The appearance of such architectures is becoming prominent in recent literature, due to the fact that the union of these two dissimilar components can give rise to a number of desirable properties that are not necessarily achieved by the individual components. For instance, while MOFs already boast unprecedented internal surface areas and highly tunable pore structures, they can often suffer from limited stability that results from the weak nature of the coordination bonding. However, recent work, outlined in this review, demonstrates that polymers can enhance MOF stability and even augment other important properties like electrical conductivity. Further, we discuss a number of other studies, where the addition of external polymer coatings or the insertion or grafting of polymer species inside the MOF pores can lead to noticeable performance enhancement in a variety of applications including water treatment, catalysis, small molecule adsorption/separation, small molecule/ion sensing, and bio-delivery. The hope is that this review will highlight the prominence of this newly emerging class of materials and demonstrate their potential in a variety of applications relevant to host–guest chemistry

Understanding your support system: the design of a stable MOF/polyazoamine support for biomass conversion

Introducing oligomeric or polymeric units into metal-organic frameworks (MOFs) can result in composites that have significantly improved properties when compared to the individual MOF or polymer building blocks. With such synergy in mind, this work presents the design of a novel MOF/polyazoamine support that is used to stabilize Pd NPs. The resulting composite catalyst, tested in the reductive amination of levulinic acid, is found to have a markedly improved lifetime when compared to just the MOF or polymer support containing Pd. It is demonstrated, for the first time, that the lifetime enhancement stems directly from the polymer, which plays a dual role: i) the oligomer stabilizes the MOF support through the elimination of certain vibrational modes associated with the framework ligand and likely pore-filling effects in the largest MOF pore, and ii) the Lewis base functionality on the oligomer backbone binds to the surface of the Pd NPs, thus, increasing their activity and inhibiting their aggregation. Several complementary spectroscopic (IR, XPS, Raman spectroscopy) and computational tools (pore space and topology analysis, molecular mechanics, and density functional theory simulations) were used to describe the nature of the MOF-oligomer interaction and identify the most likely location of the polymer within the MOF pore

An In-Situ Neutron Diffraction and DFT Study of Hydrogen Adsorption in a Sodalite-Type Metal-Organic Framework, Cu-BTTri

Herein we present a detailed study of the hydrogen adsorption properties of Cu‐BTTri, a robust crystalline metal–organic framework containing open metal‐coordination sites. Diffraction techniques, carried out on the activated framework, reveal a structure that is different from what was previously reported. Further, combining standard hydrogen adsorption measurements with in‐situ neutron diffraction techniques provides molecular level insight into the hydrogen adsorption process. The diffraction experiments unveil the location of four D2 adsorption sites in Cu‐BTTri and shed light on the structural features that promote hydrogen adsorption in this material. Density functional theory (DFT), used to predict the location and strength of binding sites, corroborate the experimental findings. By decomposing binding energies in different sites in various energetic contributions, we show that van der Waals interactions play a crucial role, suggesting a possible route to enhancing the binding energy around open metal coordination sites

A metal-organic framework/polymer derived catalyst containing single-atom nickel species for electrocatalysis

While metal-organic frameworks (MOF) alone offer a wide range of structural tunability, the formation of composites, through the introduction of other non-native species, like polymers, can further broaden their structure/property spectrum. Here we demonstrate that a polymer, placed inside the MOF pores, can support the collapsible MOF and help inhibit the aggregation of nickel during pyrolysis; this leads to the formation of single atom nickel species in the resulting nitrogen doped carbons, and dramatically improves the activity, CO selectivity and stability in electrochemical CO(2)reduction reaction. Considering the vast number of multifarious MOFs and polymers to choose from, we believe this strategy can open up more possibilities in the field of catalyst design, and further contribute to the already expansive set of MOF applications

Preparation of Highly Porous Metal-Organic Framework Beads for Metal Extraction from Liquid Streams

Metal-organic frameworks (MOFs) offer great promise in a variety of gas- and liquid-phase separations. However, the excellent performance on the lab scale hardly translates into pilot- or industrial-scale applications due to the microcrystalline nature of MOFs. Therefore, the structuring of MOFs into pellets or beads is a highly solicited and timely requirement. In this work, a general structuring method is developed for preparing MOF-polymer composite beads based on an easy polymerization strategy. This method adopts biocompatible, biodegradable poly(acrylic acid) (PAA) and sodium alginate monomers, which are cross-linked using Ca2+ ions. Also, the preparation procedure employs water and hence is nontoxic. Moreover, the universal method has been applied to 12 different structurally diverse MOFs and three MOF-based composites. To validate the applicability of the structuring method, beads consisting of a MOF composite, namely Fe-BTC/PDA, were subsequently employed for the extraction of Pb and Pd ions from real-world water samples. For example, we find that just 1 g of Fe-BTC/PDA beads is able to decontaminate >10 L of freshwater containing highly toxic lead (Pb) concentrations of 600 ppb while under continuous flow. Moreover, the beads offer one of the highest Pd capacities to date, 498 mg of Pd per gram of composite bead. Furthermore, large quantities of Pd, 7.8 wt %, can be readily concentrated inside the bead while under continuous flow, and this value can be readily increased with regenerative cycling