NMR Investigation into the Influence of Surface Interactions on Liquid Diffusion in a Mesoporous Catalyst Support

Robinson, Neil; D’Agostino, Carmine

doi:10.1007/s11244-019-01209-7

Cited by 21 publications

(18 citation statements)

References 43 publications

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“…Any inter-particle liquid was again removed from these samples, such that all observed relaxation populations must arise from the confined fluids within the silica pore network. These peaks cannot be assigned to the presence of multiple pore environments with varying surface-to-volume ratios (see Equation ( 1)), which, given the similar self-diffusion properties of shortchain alcohols and acids to our aprotic adsorbates (demonstrated elsewhere [49][50][51] ) would also be apparent within the cyclohexane and acetone data in Figure 1. Proton-proton scalar coupling artefacts 52 may also be discounted due to the very short echo time employed in these measurements (see Methods).…”

Section: Relaxation Of Polar-protic Adsorbatesmentioning

confidence: 88%

Low-Field Functional Group Resolved Nuclear Spin Relaxation in Mesoporous Silica

Robinson

May

Johns

2021

ACS Appl. Mater. Interfaces

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Solid-fluid interactions underpin the efficacy of functional porous materials across a diverse array of chemical reaction and separation processes. Here we report low magnetic field 2D 1 H nuclear spin relaxation measurements as a non-invasive probe of adsorbate identity and interfacial dynamics within such systems.For the first time, we demonstrate the capacity of this approach in distinguishing functional group-specific relaxation phenomena across a diverse range of alcohols and carboxylic acids employed as solvents, reagents and liquid hydrogen carriers, with distinct relaxation responses assigned to the alkyl and hydroxyl moieties of each confined liquids. Uniquely, this relaxation behaviour is shown to correlate with adsorbate acidity, with the observed relationship rationalised on the basis of surface-adsorbate proton exchange dynamics. Our results demonstrate that nuclear spin relaxation provides a molecular-level perspective on sorbent/sorbate interactions, motivating the exploration of such measurements as a unique probe of adsorbate identity within optically opaque porous media.

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Section: Relaxation Of Polar-protic Adsorbatesmentioning

confidence: 88%

Low-Field Functional Group Resolved Nuclear Spin Relaxation in Mesoporous Silica

Robinson

May

Johns

2021

ACS Appl. Mater. Interfaces

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“…Any inter-particle liquid was again removed from these samples, such that all observed relaxation populations must arise from the confined fluids within the silica pore network. We note these peaks cannot be assigned to the presence of multiple pore environments with varying surface-to-volume ratios (see Equation ( 1)), which, given the similar self-diffusion properties of short-chain alcohols and acids to our aprotic adsorbates (demonstrated elsewhere [49][50][51] ) would also be apparent within the cyclohexane and acetone data in Figure 1. Proton-proton scalar coupling artefacts 52 may also be discounted due to the very short echo time employed in these measurements (see Methods).…”

Section: Relaxation Of Polar-protic Adsorbatesmentioning

confidence: 88%

Functional Group Resolved Nuclear Spin Relaxation in Porous Media

Robinson

May²,

Johns³

2021

Preprint

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Understanding solid-fluid interactions within porous materials is critical for their efficient utilisation across chemical reaction and separation processes. However, detailed characterisation of interfacial phenomena within such systems is hampered by their optically opaque nature. Motivated by the need to bridge this capability gap, we detail here the application of low magnetic field 2D 1H nuclear spin relaxation measurements as a non-invasive probe of sorbate/sorbent interactions, exploring the relaxation characteristics exhibited by liquid adsorbates confined to a model mesoporous silica. For the first time, we demonstrate the capacity of such measurements to distinguish functional group-specific relaxation phenomena across a diverse range of protic adsorbates of wide importance as solvents, reagents, and hydrogen carriers, with distinct relaxation environments assigned to the alkyl and hydroxyl moieties of the confined liquids. Uniquely, this relaxation behaviour is shown to correlate with adsorbate acidity, with the observed relationship rationalised on the basis of surface-adsorbate proton exchange dynamics.

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“…NMR relaxation and diffusion experiments are powerful methods for the noninvasive investigation of adsorption and transport phenomena occurring within optically-opaque porous catalysis materials. [77][78][79] Low-field 1 H relaxation-exchange correlation measurements are applied to elucidate the dominant diffusive pathways present throughout our hierarchically porous MM-SBA-15 framework. The NMR pulse sequence for these experiments (Supplementary Figure 14) is detailed elsewhere, 81,82 and comprises two correlated measurements of the transverse nuclear spin relaxation time constant T2 either side of a mixing time of length tmix.…”

Section: Molecular Transport: Low-field Nmr Relaxation-exchange Corrementioning

confidence: 99%

A Spatially Orthogonal Hierarchically Porous Acid-Base Catalyst for Cascade and Antagonistic Reactions

Isaacs¹,

Parlett²,

Robinson³

et al. 2020

Preprint

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Complex organic molecules are of great importance to academic and industrial chemistry and typically synthesised from smaller building blocks by multistep reactions. The ability to perform multiple (distinct) transformations in a single reactor would greatly reduce the number of manipulations required for chemical manufacturing, and hence the development of multifunctional catalysts for such one-pot reactions is highly desirable. Here we report the synthesis of a hierarchically porous framework, in which the macropores are selectively functionalised with a sulfated zirconia solid acid coating, while the mesopores are selectively functionalised with MgO solid base nanoparticles. Active site compartmentalisation and substrate channelling protects base catalysed triacylglyceride transesterification from poisoning by free fatty acid impurities (even at 50 mol%), and promotes the efficient two-step cascade deacetylation-Knoevenagel condensation of dimethyl acetals to cyanoates.

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NMR Investigation into the Influence of Surface Interactions on Liquid Diffusion in a Mesoporous Catalyst Support

Cited by 21 publications

References 43 publications

Low-Field Functional Group Resolved Nuclear Spin Relaxation in Mesoporous Silica

Low-Field Functional Group Resolved Nuclear Spin Relaxation in Mesoporous Silica

Functional Group Resolved Nuclear Spin Relaxation in Porous Media

A Spatially Orthogonal Hierarchically Porous Acid-Base Catalyst for Cascade and Antagonistic Reactions

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