Chemical shaping of CPO-27-M (M = Co, Ni) through an in situ crystallization within chitosan hydrogels.

The preparation of MOF composites is considered as an effective method to address the challenges of shaping MOFs and to create porous solids with enhanced properties and broader applications. In this study, CPO-27-Co was crystallized via a simple strategy within porous chitosan beads. The resulting CS@CPO-27-Co composites were tested for CO2 sorption and they demonstrated promising performances by exceeding 3 mmol(CO2) g-1. The versatility of this strategy was further demonstrated by replacing cobalt(II) ions with nickel(II), also leading to the isostructural CPO-27 framework.

SBA-15 supported Ni-Cu catalysts for hydrodeoxygenation of m-cresol to toluene.

Amidst concerns over fossil fuel dependency and environmental sustainability, the utilization of biomass-derived aromatic compounds emerges as a viable solution across diverse industries. In this scheme, the conversion of biomass involves pyrolysis, followed by a hydrodeoxygenation (HDO) step to reduce the oxygen content of pyrolysis oils and stabilize the end products including aromatics. In this study, we explored the properties of size controlled NiCu bimetallic catalysts supported on ordered mesoporous silica (SBA-15) for the catalytic gas-phase HDO of m-cresol, a lignin model compound. We compared their performances with monometallic Ni and Cu catalysts. The prepared catalysts contained varying Ni to Cu ratios and featured an average particle size of approximately 2 nm. The catalytic tests revealed that the introduction of Cu alongside Ni enhanced the selectivity for the direct deoxygenation (DDO) pathway, yielding toluene as the primary product. Optimal performance was observed with a catalyst composition comprising 5 wt.% Ni and 5 wr.% Cu, achieving 85 % selectivity to toluene. Further increasing the Cu content improved turnover frequency (TOF) values, but reduced DDO selectivity. These findings underscore the importance of catalyst design in facilitating biomass-derived compound transformations and offer insights into optimizing catalyst composition for more selective HDO reactions.

Borophene: a piezocatalyst for water remediation.

Borophene is an emerging two-dimensional material exhibiting exceptional piezocatalytic activity under the influence of ultrasonic vibrations, as exemplified herein by the decomposition of highly stable organic dyes in water. After 6 minutes of exposure, borophene sheets converted up to 92 percent of a mixture of dye molecules at room temperature.

Carbon-Supported Ru-Ni and Ru-W Catalysts for the Transformation of Hydroxyacetone and Saccharides into Glycol-Derived Primary Amines.

Nitrogen-containing molecules are used for the synthesis of polymers, surfactants, agrochemicals, and dyes. In the context of green chemistry, it is important to form such compounds from bioresource. Short-chain primary amines are of interest for the polymer industry, like 2-aminopropanol, 1-aminopropan-2-ol, and 1,2-diaminopropane. These amines can be formed through the amination of oxygenated substrates, preferably in aqueous phase. This is possible with heterogeneous catalysts, however, effective systems that allow reactions under mild conditions are lacking. We report an efficient catalyst Ru-Ni/AC for the reductive amination of hydroxyacetone into 2-aminopropanol. The catalyst has been reused during 3 cycles demonstrating a good stability. As a prospective study, extension to the reactivity of (poly)carbohydrates has been realized. Despite a lesser efficiency, 2-aminopropanol (9 % yield of amines) has been formed from fructose, the first example from a carbohydrate. This was possible using a 7.5 %Ru-36 %WxC/AC catalyst, composition allowing a one-pot retro-aldol cleavage into hydroxyacetone and reductive amination. The transformation of cellulose through sequential reactions with a combination of 30 %W2C/AC and 7.5 %Ru-36 %WxC/AC system gave 2 % of 2-aminopropanol, corresponding to the first example of the formation of this amine from cellulose with heterogeneous catalysts.

Stability of Iodine Species Trapped in Titanium-Based MOFs: MIL-125 and MIL-125_NH2.

Two titanium-based MOFs MIL-125 and MIL-125_NH2 are synthesized and characterized using high-temperature powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), N2 sorption, Fourier transformed infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet-visible spectroscopy (UV-Vis), and electron paramagnetic resonance (EPR). Stable up to 300 °C, both compounds exhibited similar specific surface areas (SSA) values (1207 and 1099 m2 g-1 for MIL-125 and MIL-125_NH2, respectively). EPR signals of Ti3+ are observed in both, whith MIL-125_NH2 also showing ─NH2 ●+ signatures. Both MOFs efficiently adsorbed iodine in continuous gas flow over five days, with MIL-125 trapping 1.9 g.g-1 and MIL-125_NH2 trapping 1.6 g.g-1. MIL-125_NH2 exhibited faster adsorption kinetics due to its smaller band gap (2.5 against 3.6 eV). In situ Raman spectroscopy conducted during iodine adsorption revealed signal evolution from "free" I2 to "perturbed" I2, and I3 -. TGA and in situ Raman desorption experiments showed that ─NH2 groups improved the stabilization of I3 - due to an electrostatic interaction with NH2 ●+BDC radicals. The Albery model indicated longer lifetimes for iodine desorption in I2@MIL-125_NH2, attributed to a rate-limiting step due to stronger interaction between the anionic iodine species and the ─NH2 ●+ radicals. This study underscores how MOFs with efficient charge separation and hole-stabilizer functional groups enhance iodine stability at higher temperatures.

Green synthesis of MOF-based textile composites for the degradation of a chemical warfare agent simulant.

A green synthesis of UiO-66-NH2 embedded in chitosan and deposited on textiles has been investigated for the degradation of chemical warfare agents. This method requires no heating or use of toxic solvents. The composite synthesized presents an interesting efficiency in detoxifying common simulants of chemical warfare agents, such as DMNP. In parallel, resistance and permeability tests were also realized in order to confirm the suitability of the composites for further applications.

Enhanced Gas Adsorption in HKUST-1@Chitosan Aerogels, Cryogels, and Xerogels: An Evaluation Study.

This study investigates the use of chitosan hydrogel microspheres as a template for growing an extended network of MOF-type HKUST-1. Different drying methods (supercritical CO2, freeze-drying, and vacuum drying) were used to generate three-dimensional polysaccharide nanofibrils embedding MOF nanoclusters. The resulting HKUST-1@Chitosan beads exhibit uniform and stable loadings of HKUST-1 and were used for the adsorption of CO2, CH4, Xe, and Kr. The maximum adsorption capacity of CO2 was found to be 1.98 mmol·g-1 at 298 K and 1 bar, which is significantly higher than those of most MOF-based composite materials. Based on Henry's constants, thus-prepared HKUST-1@CS beads also exhibit fair selectivity for CO2 over CH4 and Xe over Kr, making them promising candidates for capture and separation applications.

Milling-Assisted Loading of Drugs into Mesoporous Silica Carriers: A Green and Simple Method for Obtaining Tunable Customized Drug Delivery.

Mesoporous silica (MPS) carriers are considered as a promising strategy to increase the solubility of poorly soluble drugs and to stabilize the amorphous drug delivery system. The development by the authors of a solvent-free method (milling-assisted loading, MAL) made it possible to manipulate the physical state of the drug within the pores. The present study focuses on the effects of the milling intensity and the pore architecture (chemical surface) on the physical state of the confined drug and its release profile. Ibuprofen (IBP) and SBA-15 were used as the model drug and the MPS carrier, respectively. It was found that decreasing the milling intensity promotes nanocrystallization of confined IBP. Scanning electron microscopy and low-frequency Raman spectroscopy investigations converged into a bimodal description of the size distribution of particles, by decreasing the milling intensity. The chemical modification of the pore surface with 3-aminopropyltriethoxisylane also significantly promoted nanocrystallization, regardless of the milling intensity. Combined analyses of drug release profiles obtained on composites prepared from unmodified and modified SBA-15 with various milling intensities showed that the particle size of composites has the greatest influence on the drug release profile. Tuning drug concentration, milling intensity, and chemical surface make it possible to easily customize drug delivery.

Extrusion-Spheronization of UiO-66 and UiO-66_NH2 into Robust-Shaped Solids and Their Use for Gaseous Molecular Iodine, Xenon, and Krypton Adsorption.

The use of an extrusion-spheronization process was investigated to prepare robust and highly porous extrudates and granules starting from UiO-66 and UiO-66_NH2 metal-organic framework powders. As-produced materials were applied to the capture of gaseous iodine and the adsorption of xenon and krypton. In this study, biosourced chitosan and hydroxyethyl cellulose (HEC) are used as binders, added in low amounts (less than 5 wt % of the dried solids), as well as a colloidal silica as a co-binder when required. Characterizations of the final shaped materials reveal that most physicochemical properties are retained, except the textural properties, which are impacted by the process and the proportion of binders (BET surface area reduction from 5 to 33%). On the other hand, the mechanical resistance of the shaped materials toward compression is greatly improved by the presence of binders and their respective contents, from 0.5 N for binderless UiO-66 granules to 17 N for UiO-66@HEC granules. UiO-66_NH2-based granules demonstrated consequent iodine capture after 48 h, up to 527 mg/g, in line with the pristine UiO-66_NH2 powder (565 mg/g) and proportionally to the retaining BET surface area (-5% after shaping). Analogously, the shaped materials presented xenon and krypton sorption isotherms correlated to their BET surface area and high predicted xenon/krypton selectivity, from 7.1 to 9.0. Therefore, binder-aided extrusion-spheronization is an adapted method to produce shaped solids with adequate mechanical resistance and retained functional properties.

Stability and radioactive gaseous iodine-131 retention capacity of binderless UiO-66-NH2 granules under severe nuclear accidental conditions.

In the present work, we aim to investigate the ability of the zirconium-based MOF-type compound UiO-66-NH2, to immobilize molecular gaseous iodine under conditions analogous to those encountered in an operating Filtered Containment Venting System (FCVS) line. Typically, the UiO-66-NH2 particles were exposed to 131I (beta and gamma emitters) and submitted to air/steam at 120 °C, under gamma irradiation (1.9 kGy h-1). In parallel to this experiment under simulated accidental conditions, the stability of the binderless UiO-66-NH2 granules under steam and gamma irradiation was investigated. In order to fit with the specifications required by typical venting systems, and to compare the efficiency of the selected MOF to porous materials commonly used by the industry, scale-up syntheses and UiO-66-NH2 millimetric-size shaping were realized. For this task, we developed an original binderless method, in order to analyze solely the efficiency of the UiO-66-NH2 material. The shaped MOF particles were then submitted separately to gamma irradiation, steam and temperature, for confirming their viability in a venting process. Their structural, textural and mechanical behaviors were characterized by the means several techniques including gas sorption, powder X-ray diffraction, infrared spectroscopy and crushing tests. Promising results were obtained to trap gaseous molecular iodine in severe accidental conditions.

Manipulating the physical states of confined ibuprofen in SBA-15 based drug delivery systems obtained by solid-state loading: Impact of the loading degree.

Using the Milling-Assisted Loading (MAL) solid-state method for loading a poorly water-soluble drug (ibuprofen, IBP) within the SBA-15 matrix has given the opportunity to manipulate the physical state of drugs for optimizing bioavailability. The MAL method makes it easy to control and analyze the influence of the degree of loading on the physical state of IBP inside the SBA-15 matrix with an average pore diameter of 9.4 nm. It was found that the density of IBP molecules in an average pore size has a direct influence on both the glass transition and the mechanism of crystallization. Detailed analyzes of the crystallite distribution and melting by Raman mapping, x-ray diffraction, and differential scanning calorimetry have shown that the crystals are localized in the core of the channel and surrounded by a liquid monolayer. The results of these complementary investigations have been used for determining the relevant parameters (related to the SBA-15 matrix and to the IBP molecule) and the nature of the physical state of the confined matter.

Formulation of Metal-Organic Framework Inks for the 3D Printing of Robust Microporous Solids toward High-Pressure Gas Storage and Separation.

The shaping of metal-organic frameworks (MOFs) has become increasingly studied over the past few years, because it represents a major bottleneck toward their further applications at a larger scale. MOF-based macroscale solids should present performances similar to those of their powder counterparts, along with adequate mechanical resistance. Three-dimensional printing is a promising technology as it allows the fast prototyping of materials at the macroscale level; however, the large amounts of added binders have a detrimental effect on the porous properties of the solids. Herein, a 3D printer was modified to prepare a variety of MOF-based solids with controlled morphologies from shear-thinning inks containing 2-hydroxyethyl cellulose. Four benchmark MOFs were tested for this purpose: HKUST-1, CPL-1, ZIF-8, and UiO-66-NH2. All solids are mechanically stable with up to 0.6 MPa of uniaxial compression and highly porous with BET specific surface areas lowered by 0 to -25%. Furthermore, these solids were applied to high-pressure hydrocarbon sorption (CH4, C2H4, and C2H6), for which they presented a consequent methane gravimetric uptake (UiO-66-NH2, ZIF-8, and HKUST-1) and a highly preferential adsorption of ethylene over ethane (CPL-1).

Freezing-induced ordering of block copolymer micelles.

We demonstrate here the ordering of block copolymer micelles by ice templating, below 0 °C. We used this for the preparation of silica monoliths that present an ice-templated macroporosity, combined with a 2D hexagonal mesostructure templated by the addition of P123. We propose a mechanism triggered by the progressive freezing-induced concentration.

An efficient route to highly organized, tunable macroporous-mesoporous alumina.

Organized macroporous-mesoporous alumina can be obtained via a dual-templating approach. Monodispersed polystyrene beads promote macropore formation, while a P123 surfactant templating agent drives the formation of ordered hexagonal mesopores throughout the alumina framework. These well-defined pore networks coexist over a wide range of temperatures and macropore sizes.