Designing inhalable metal organic frameworks for pulmonary tuberculosis treatment and theragnostics via spray drying.

Inhalable metal organic framework (MOF) aerosols have been developed via spray drying as a therapy for multi-drug resistant (MDR) tuberculosis (TB). The CuPOA2 (pyrazinoate acid) MOFs can be tailored to exhibit a respirable mass median aerodynamic diameter (MMAD) of 2.6 µm. This method is repeated to manufacture Gd0.1Cu0.9(POA)2 MOFs for inhalable theragnostics.

Thermal Defect Engineering of Precious Group Metal-Organic Frameworks: A Case Study on Ru/Rh-HKUST-1 Analogues.

A methodology is introduced for controlled postsynthetic thermal defect engineering (TDE) of precious group metal-organic frameworks (PGM-MOFs). The case study is based on the Ru/Rh analogues of the archetypical structure [Cu3(BTC)2] (HKUST-1; BTC = 1,3,5-benzenetricarboxylate). Quantitative monitoring of the TDE process and extensive characterization of the samples employing a complementary set of analytical and spectroscopic techniques reveal that the compositionally very complex TDE-MOF materials result from the elimination and/or fragmentation of ancillary ligands and/or linkers. TDE involves the preferential secession of acetate ligands, intrinsically introduced via coordination modulation during synthesis, and the gradual decarboxylation of ligator sites of the framework linker BTC. Both processes lead to modified Ru/Rh paddlewheel nodes. These nodes exhibit a lowered average oxidation state and more accessible open metal centers, as deduced from surface-ligand IR spectroscopy using CO as a probe and supported by density functional theory (DFT)-based computations. The monometallic and the mixed-metal PGM-MOFs systematically differ in their TDE properties and, in particular in the hydride generation ability (HGA). This latter property is an important indicator for the catalytic activity of PGM-MOFs, as demonstrated by the ethylene dimerization reaction to 1-butene.

Gas reactions under intrapore condensation regime within tailored metal-organic framework catalysts.

Production of 1-butene, a major monomer in polymer industry, is dominated by homogeneous protocols via ethylene dimerization. Homogeneous catalysts can achieve high selectivity but require large amounts of activators and solvents, and exhibit poor recyclability; in turn, heterogeneous systems are robust but lack selectivity. Here we show how the precise engineering of metal-organic frameworks (MOFs) holds promise for a sustainable process. The key to the (Ru)HKUST-1 MOF activity is the intrapore reactant condensation that enhances ethylene dimerization with high selectivity (> 99% 1-butene) and high stability (> 120 h) in the absence of activators and solvents. According to spectroscopy, kinetics, and modeling, the engineering of defective nodes via controlled thermal approaches rules the activity, while intrapore ethylene condensation accounts for selectivity and stability. The combination of well-defined actives sites with the concentration effect arising from condensation regimes paves the way toward the development of robust MOF catalysts for diverse gas-phase reactions.

Synthesis of Soluble Metal Organic Framework Composites for Mixed Matrix Membranes.

A general, green, efficient, and easily scalable methodology has been developed to more effectively incorporate (disperse) metal-organic frameworks (MOFs) into polymer technologies via solid state synthesis of any MOF nanocrystals within soluble mesoporous polymers. The resulting solid hybrid materials (pellets) can be directly transformed into colloidal MOF polymeric suspensions (inks) by simple dissolution in organic solvents. The straightforward use of novel colloidal MOF polymeric inks as ultimate additive for mixed matrix membranes resulted in unprecedented snakeskin microstructure exhibiting outstanding selectivity for CO2 over N2 (>100) from post-combustion flue gas at very low and well-dispersed MOF nanocrystal concentrations ranging from 1 to 7 wt %. This novel methodology brings one of the most versatile routes yet reported to transform any MOF into more functional forms that can be directly integrated into any conventional polymer technology at the commercial scale.

Transformation of single MOF nanocrystals into single nanostructured catalysts within mesoporous supports: a platform for pioneer fluidized-nanoreactor hydrogen carriers.

Well-dispersed nanostructured catalysts along mesoporous materials have been systematically prepared via a novel multistep approach involving either the pyrolysis under nitrogen, the calcination under oxygen or the reduction under hydrogen of MOF nanocrystals decorated with transition metal complexes and previously confined within the mesoporous cavities via novel solid state synthesis. The resulting supported nanostructured catalysts can be composed of metals, metal oxides, heteroatom-doped carbons and combinations thereof depending on the transformation conditions. The pioneering concept of Fluidized-Nanoreactor Hydrogen Carriers has been proposed for the first time by using the resulting nanostructured catalysts within fluidized mesoporous silica.

Flying MOFs: polyamine-containing fluidized MOF/SiO2 hybrid materials for CO2 capture from post-combustion flue gas.

Solid-state synthesis ensures a high loading and well-dispersed growth of a large collection of metal-organic framework (MOF) nanostructures within a series of commercially available mesoporous silica. This approach provides a general, highly efficient, scalable, environmentally friendly, and inexpensive strategy for shaping MOFs into a fluidized form, thereby allowing their application in fluidized-bed reactors for diverse applications, such as CO2 capture from post-combustion flue gas. A collection of polyamine-impregnated MOF/SiO2 hybrid sorbents were evaluated for CO2 capture under simulated flue gas conditions in a packed-bed reactor. Hybrid sorbents containing a moderate loading of (Zn)ZIF-8 are the most promising sorbents in terms of CO2 adsorption capacity and long-term stability (up to 250 cycles in the presence of contaminants: SO2, NO x and H2S) and were successfully prepared at the kilogram scale. These hybrid sorbents demonstrated excellent fluidizability and performance under the relevant process conditions in a visual fluidized-bed reactor. Moreover, a biochemically inspired strategy for covalently linking polyamines to MOF/SiO2 through strong phosphine bonds has been first introduced in this work as a powerful and highly versatile post-synthesis modification for MOF chemistry, thus providing a novel alternative towards more stable CO2 solid sorbents.

Synthesis of Fluidized CO2 Sorbents Based on Diamine Coordinated to Metal-Organic Frameworks by Direct Conversion of Metal Oxides Supported on Mesoporous Silica.

A general and efficient method for shaping MOFs into fluidized forms has been developed by direct conversion of metal oxides supported on fluidized mesoporous silica. The resulting fluidized MOF hybrid materials containing diamines coordinated at the open metal sites have been studied as CO2 solid sorbents from post-combustion flue gas showing similar performance than their bulk counterparts. These new fluidized MOF hybrid materials can be used for other applications involving fluidized bed reactor configurations, in which MOFs have never been considered.

Boosting the Catalytic Performance of Metal-Organic Frameworks for Steroid Transformations by Confinement within a Mesoporous Scaffold.

Solid-state crystallization achieves selective confinement of metal-organic framework (MOF) nanocrystals within mesoporous materials, thereby rendering active sites more accessible compared to the bulk-MOF and enhancing the chemical and mechanical stability of MOF nanocrystals. (Zr)UiO-66(NH2 )/SiO2 hybrid materials were tested as efficient and reusable heterogeneous catalysts for the synthesis of steroid derivatives, outperforming the bulk (Zr)UiO-66(NH2 ) MOF. A clear correlation between the catalytic activity of the dispersed Zr sites present in the confined MOF, and the loading of the mesoporous SiO2 , is demonstrated for steroid transformations.

Metal-organic framework nanosheets in polymer composite materials for gas separation.

Composites incorporating two-dimensional nanostructures within polymeric matrices have potential as functional components for several technologies, including gas separation. Prospectively, employing metal-organic frameworks (MOFs) as versatile nanofillers would notably broaden the scope of functionalities. However, synthesizing MOFs in the form of freestanding nanosheets has proved challenging. We present a bottom-up synthesis strategy for dispersible copper 1,4-benzenedicarboxylate MOF lamellae of micrometre lateral dimensions and nanometre thickness. Incorporating MOF nanosheets into polymer matrices endows the resultant composites with outstanding CO2 separation performance from CO2/CH4 gas mixtures, together with an unusual and highly desired increase in the separation selectivity with pressure. As revealed by tomographic focused ion beam scanning electron microscopy, the unique separation behaviour stems from a superior occupation of the membrane cross-section by the MOF nanosheets as compared with isotropic crystals, which improves the efficiency of molecular discrimination and eliminates unselective permeation pathways. This approach opens the door to ultrathin MOF-polymer composites for various applications.

Multifunctional, defect-engineered metal-organic frameworks with ruthenium centers: sorption and catalytic properties.

A mixed-linker solid-solution approach was employed to modify the metal sites and introduce structural defects into the mixed-valence Ru(II/III) structural analogue of the well-known MOF family [M3(II,II)(btc)2] (M=Cu, Mo, Cr, Ni, Zn; btc=benzene-1,3,5-tricarboxylate), with partly missing carboxylate ligators at the Ru2 paddle-wheels. Incorporation of pyridine-3,5-dicarboxylate (pydc), which is the same size as btc but carries lower charge, as a second, defective linker has led to the mixed-linker isoreticular derivatives of Ru-MOF, which display characteristics unlike those of the defect-free framework. Along with the creation of additional coordinatively unsaturated sites, the incorporation of pydc induces the partial reduction of ruthenium. Accordingly, the modified Ru sites are responsible for the activity of the "defective" variants in the dissociative chemisorption of CO2, the enhanced performance in CO sorption, the formation of hydride species, and the catalytic hydrogenation of olefins.

Water stable Zr-benzenedicarboxylate metal-organic frameworks as photocatalysts for hydrogen generation.

The Zr-containing metal-organic frameworks (MOFs) formed by terephthalate (UiO-66) and 2-aminoterephthalate ligands [UiO-66(NH(2))] are two notably water-resistant MOFs that exhibit photocatalytic activity for hydrogen generation in methanol or water/methanol upon irradiation at wavelength longer than 300 nm. The apparent quantum yield for H(2) generation using monochromatic light at 370 nm in water/methanol 3:1 was of 3.5% for UiO-66(NH(2)). Laser-flash photolysis has allowed detecting for UiO-66 and UiO-66(NH(2)) the photochemical generation of a long lived charge separated state whose decay is not complete 300 µs after the laser flash. Our finding and particularly the influence of the amino group producing a bathochromic shift in the optical spectrum without altering the photochemistry shows promises for the development of more efficient MOFs for water splitting.