Green Synthesis of MOF-Based Materials for Electrochemical Reduction of Carbon Dioxide.

Porous ZIF-8 and ZIF-67 were synthesized via a green steam-assisted dry-gel technique and investigated as potential catalysts for CO electroreduction. The synthesis conditions are found to significantly influence the growth of these metal-organic frameworks (MOFs). Notably, the water content employed during synthesis plays a crucial role in shaping the morphological properties of ZIF-8.

Detection of helical water flows in sub-nanometer channels.

Nanoscale flows of liquids can be revealed in various biological processes and underlie a wide range of nanofluidic applications. Though the integral characteristics of these systems, such as permeability and effective diffusion coefficient, can be measured in experiments, the behaviour of the flows within nanochannels is still a matter of speculation. Herein, we used a combination of quadrupolar solid-state NMR spectroscopy, computer simulation, and dynamic vapour sorption measurements to analyse water diffusion inside peptide nanochannels.

Valorization of Crab Shells as Potential Sorbent Materials for CO Capture.

This study delves into the potential advantage of utilizing crab shells as sustainable solid adsorbents for CO capture, offering an environmentally friendly alternative to conventional porous adsorbents, such as zeolites, silicas, metal-organic frameworks (MOFs), and porous carbons. The investigation focuses on crab shell waste, which exhibits inherent natural porosity and N-bearing groups, making them promising candidates for CO physisorption and chemisorption applications. Selective deproteinization and demineralization treatments were used to enhance textural properties while preserving the natural porous structure of the crab shells.

Unravelling the structure of CO in silica adsorbents: an NMR and computational perspective.

This comprehensive review describes recent advancements in the use of solid-state NMR-assisted methods and computational modeling strategies to unravel gas adsorption mechanisms and CO speciation in porous CO-adsorbent silica materials at the atomic scale. This work provides new perspectives for the innovative modifications of these materials rendering them more amenable to the use of advanced NMR methods.

Covalent connectivity of glycogen in brewer's spent yeast cell walls revealed by enzymatic approaches and dynamic nuclear polarization NMR.

Yeast cell walls undergo modifications during the brewing process, leading to a remodelling of their architecture. One significant change is the increased insolubility of the cell wall glycogen pool, likely due to the formation of covalent bonds between glycogen and cell wall polysaccharides. To verify this hypothesis, we extracted the brewer's spent yeast with 4 M KOH, obtaining an insoluble glucan fraction (AE.

One-Shot Resin 3D-Printed Stators for Low-Cost Fabrication of Magic-Angle Spinning NMR Probeheads.

Additive manufacturing such as three-dimensional (3D)-printing has revolutionized the fast and low-cost fabrication of otherwise expensive NMR parts. High-resolution solid-state NMR spectroscopy demands rotating the sample at a specific angle (54.74°) inside a pneumatic turbine, which must be designed to achieve stable and high spinning speeds without mechanical friction.

Engineering phosphatidylinositol-4,5-bisphosphate model membranes enriched in endocytic cargo: A neutron reflectometry, AFM and QCM-D structural study.

The combination of in vitro models of biological membranes based on solid-supported lipid bilayers (SLBs) and of surface sensitive techniques, such as neutron reflectometry (NR), atomic force microscopy (AFM) and quartz crystal microbalance with dissipation monitoring (QCM-D), is well suited to provide quantitative information about molecular level interactions and lipid spatial distributions. In this work, cellular plasma membranes have been mimicked by designing complex SLB, containing phosphatidylinositol 4,5-bisphosphate (PtdIns4,5P) lipids as well as incorporating synthetic lipo-peptides that simulate the cytoplasmic tails of transmembrane proteins. The QCM-D results revealed that the adsorption and fusion kinetics of PtdIns4,5P are highly dependent of Mg.

Assessing CO Capture in Porous Sorbents via Solid-State NMR-Assisted Adsorption Techniques.

Adsorption isotherms obtained through volumetric measurements are widely used to estimate the gas adsorption performance of porous materials. Nonetheless, there is always ambiguity regarding the contributions of chemi- and physisorption processes to the overall retained gas volume. In this work, we propose, for the first time, the use of solid-state NMR (ssNMR) to generate isotherms of CO adsorbed onto an amine-modified silica sorbent.

Exploring Molecular Dynamics of Adsorbed CO Species in Amine-Modified Porous Silica by Solid-State NMR Relaxation.

Previous studies on CO adsorbents have mainly addressed the identification and quantification of adsorbed CO species in amine-modified porous materials. Investigation of molecular motion of CO species in confinement has not been explored in depth yet. This work entails a comprehensive study of molecular dynamics of the different CO species chemi- and physisorbed at amine-modified silica materials through the determination of the rotating frame spin-lattice relaxation times ( ) by solid-state NMR.

Elucidating the Nature of the External Acid Sites of ZSM-5 Zeolites Using NMR Probe Molecules.

The identification of acid and nonacid species at the external surface of zeolites remains a major challenge, in contrast to the extensively-studied internal acid sites. Here, it is shown that the synthesis of zeolite ZSM-5 samples with distinct particle sizes, combined with solid-state NMR and computational studies of trimethylphosphine oxide (TMPO) adsorption, provides insight into the chemical species on the external surface of the zeolite crystals. H- P HETCOR NMR spectra of TMPO-loaded zeolites exhibit a broad correlation peak at δ ∼35-55 ppm and δ ∼5-12 ppm assigned to external SiOH species.

Elucidating the Germanium Distribution in ITQ-13 Zeolites by Density Functional Theory.

ITQ-13 is a medium-pore zeolite that can be prepared in all-silica form and as silicogermanate with Si/Ge ratios as low as 3. Usually synthesised in the presence of fluoride, ITQ-13 is among the very few systems containing fluoride anions in two distinct cage types, cube-like d4r units and [4 ⋅ 5 ] cages. Here, dispersion-corrected density functional theory (DFT) calculations are used to investigate the energetically most favourable Ge distributions for Si/Ge ratios between 55 and 6.

Unravelling moisture-induced CO chemisorption mechanisms in amine-modified sorbents at the molecular scale.

This work entails a comprehensive solid-state NMR and computational study of the influence of water and CO partial pressures on the CO-adducts formed in amine-grafted silica sorbents. Our approach provides atomic level insights on hypothesised mechanisms for CO capture under dry and wet conditions in a tightly controlled atmosphere. The method used for sample preparation avoids the use of liquid water slurries, as performed in previous studies, enabling a molecular level understanding, by NMR, of the influence of controlled amounts of water vapor (down to 0.

"Hidden" CO in Amine-Modified Porous Silicas Enables Full Quantitative NMR Identification of Physi- and Chemisorbed CO Species.

Although spectroscopic investigation of surface chemisorbed CO species has been the focus of most studies, identifying different domains of weakly interacting (physisorbed) CO molecules in confined spaces is less trivial as they are often indistinguishable resorting to (isotropic) NMR chemical shift or vibrational band analyses. Herein, we undertake for the first time a thorough solid-state NMR analysis of CO species physisorbed prior to and after amine-functionalization of silica surfaces; combining C NMR chemical shift anisotropy (CSA) and longitudinal relaxation times ( ). These methods were used to quantitatively distinguish otherwise overlapping physisorbed CO signals, which contributed to an empirical model of CO speciation for the physi- and chemisorbed fractions.

What Is Being Measured with P-Bearing NMR Probe Molecules Adsorbed on Zeolites?

Elucidating the nature, strength, and siting of acid sites in zeolites is fundamental to fathom their reactivity and catalytic behavior. Despite decades of research, this endeavor remains a major challenge. Trimethylphosphine oxide (TMPO) has been proposed as a reliable probe molecule to study the acid properties of solid acid catalysts, allowing the identification of distinct Brønsted and Lewis acid sites and the assessment of Brønsted acid strengths.

Water-Soluble Polymeric Carbon Nitride Colloidal Nanoparticles for Highly Selective Quasi-Homogeneous Photocatalysis.

Heptazine-based polymeric carbon nitrides (PCN) are promising photocatalysts for light-driven redox transformations. However, their activity is hampered by low surface area resulting in low concentration of accessible active sites. Herein, we report a bottom-up preparation of PCN nanoparticles with a narrow size distribution (ca.

H-P HETCOR NMR elucidates the nature of acid sites in zeolite HZSM-5 probed with trimethylphosphine oxide.

Two-dimensional 1H-31P heteronuclear correlation NMR of trimethylphosphine oxide (TMPO) adsorbed in zeolites, in tandem with DFT calculations, challenges previous one-dimensional 31P NMR assignments, enabling the unambiguous discrimination of Brønsted and Lewis acid sites, extending the understanding of TMPO:Brønsted complexes formed with distinct stoichiometries at the HZSM-5 zeolite surface, and the proton-transfer mechanism.

Unravelling the Structure of Chemisorbed CO Species in Mesoporous Aminosilicas: A Critical Survey.

Chemisorbent materials, based on porous aminosilicas, are among the most promising adsorbents for direct air capture applications, one of the key technologies to mitigate carbon emissions. Herein, a critical survey of all reported chemisorbed CO species, which may form in aminosilica surfaces, is performed by revisiting and providing new experimental proofs of assignment of the distinct CO species reported thus far in the literature, highlighting controversial assignments regarding the existence of chemisorbed CO species still under debate. Models of carbamic acid, alkylammonium carbamate with different conformations and hydrogen bonding arrangements were ascertained using density functional theory (DFT) methods, mainly through the comparison of the experimental C and N NMR chemical shifts with those obtained computationally.

Hydrogen bonding networks in gabapentin protic pharmaceutical salts: NMR and in silico studies.

Hydrogen bonds (HBs) play a key role in the supramolecular arrangement of crystalline solids and, although they have been extensively studied, the influence of their strength and geometry on crystal packing remains poorly understood. Here we describe the crystal structures of two novel protic gabapentin (GBP) pharmaceutical salts prepared with the coformers methanesulfonic acid (GBP:METHA) and ethanesulfonic acid (GBP:ETHA). This study encompasses experimental and computational electronic structure analyses of H NMR chemical shifts (CSs), upon in silico HB cleavage.

Detecting Proton Transfer in CO Species Chemisorbed on Amine-Modified Mesoporous Silicas by Using C NMR Chemical Shift Anisotropy and Smart Control of Amine Surface Density.

The wealth of site-selective structural information on CO speciation, obtained by spectroscopic techniques, is often hampered by the lack of easy-to-control synthetic routes. Herein, an alternative experimental protocol that relies on the high sensitivity of C chemical shift anisotropy (CSA) tensors to proton transfer, is presented to unambiguously distinguish between ionic/charged and neutral CO species, formed upon adsorption of CO in amine-modified porous materials. Control of the surface amine spacing was achieved through the use of amine protecting groups during functionalisation prior to CO adsorption.

Structure of Chemisorbed CO(2) Species in Amine-Functionalized Mesoporous Silicas Studied by Solid-State NMR and Computer Modeling.

Two-dimensional (2D) solid-state nuclear magnetic resonance (SSNMR) experiments on samples loaded with C-labeled CO, "under controlled partial pressures", have been performed in this work, revealing unprecedented structural details about the formation of CO adducts from its reaction with various amine-functionalized SBA-15 containing amines having distinct steric hindrances (e.g., primary, secondary) and similar loadings.

A supramolecular strategy based on molecular dipole moments for high-quality covalent organic frameworks.

A supramolecular strategy based on strong molecular dipole moments is presented to gain access to covalent organic framework structures with high crystallinity and porosity. Antiparallel alignment of the molecules within the pore walls is proposed to lead to reinforced columnar stacking, thus affording a high-quality material. As a proof of principle, a novel pyrene dione building block was prepared and reacted with hexahydroxytriphenylene to form a boronic ester-linked covalent organic framework.

Chitin-glucan complex production by Komagataella pastoris: Downstream optimization and product characterization.

Purified chitin-glucan complex (CGCpure) was extracted from Komagataella pastoris biomass using a hot alkaline treatment, followed by neutralization and repeated washing with deionized water. The co-polymer thus obtained had a β-glucan:chitin molar ratio of 75:25 and low protein and inorganic salts contents (3.0 and 0.

Diazole-based powdered cocrystal featuring a helical hydrogen-bonded network: structure determination from PXRD, solid-state NMR and computer modeling.

We present the structure of a new equimolar 1:1 cocrystal formed by 3,5-dimethyl-1H-pyrazole (dmpz) and 4,5-dimethyl-1H-imidazole (dmim), determined by means of powder X-ray diffraction data combined with solid-state NMR that provided insight into topological details of hydrogen bonding connectivities and weak interactions such as CH···π contacts. The use of various 1D/2D (13)C, (15)N and (1)H high-resolution solid-state NMR techniques provided structural insight on local length scales revealing internuclear proximities and relative orientations between the dmim and dmpz molecular building blocks of the studied cocrystal. Molecular modeling and DFT calculations were also employed to generate meaningful structures.

Sulfonated graphene oxide as effective catalyst for conversion of 5-(hydroxymethyl)-2-furfural into biofuels.

The acid-catalyzed reaction of 5-(hydroxymethyl)-2-furfural with ethanol is a promising route to produce biofuels or fuel additives within the carbohydrate platform; specifically, this reaction may give 5-ethoxymethylfurfural, 5-(ethoxymethyl)furfural diethylacetal, and/or ethyl levulinate (bioEs). It is shown that sulfonated, partially reduced graphene oxide (S-RGO) exhibits a more superior catalytic performance for the production of bioEs than several other acid catalysts, which include sulfonated carbons and the commercial acid resin Amberlyst-15, which has a much higher sulfonic acid content and stronger acidity. This was attributed to the cooperative effects of the sulfonic acid groups and other types of acid sites (e.

Microwave assisted N-alkylation of amine functionalized crystal-like mesoporous phenylene-silica.

N-alkylation reaction of amine functionalized phenylene moieties in crystal-like mesoporous silica is successfully achieved with about 87% of conversion in two reaction cycles. A potassium iodide catalyzed method commonly used for the selective N-monoalkylation of aniline is adapted and optimized to the N-monoalkylation reactions of the amine functionalized periodic mesoporous phenylene-silica (NH2-PMO) under microwave irradiation with preservation of the ordered mesostructure and of the crystal-like molecular scale periodicity of the material. This functionalization opens an avenue for the preparation of new materials with different amino-alkyl groups specially designed for a desired application, namely on the adsorption or catalytic fields.