The ratio of NMR relaxation time constants T 1 / T 2 provides a non-destructive indication of the relative surface affinities exhibited by adsorbates within liquid-saturated mesoporous catalysts. In the present work we provide supporting evidence for the existence of a quantitative relationship between such measurements and adsorption energetics. As a prototypical example with relevance to green chemical processes we examine and contrast the relaxation characteristics of primary alcohols and cyclohexane within an industrial silica catalyst support. T 1 / T 2 values obtained at intermediate magnetic field strength are in good agreement with DFT adsorption energy calculations performed on single molecules interacting with an idealised silica surface. Our results demonstrate the remarkable ability of this metric to quantify surface affinities within systems of relevance to liquid-phase heterogeneous catalysis, and highlight NMR relaxation as a powerful method for the determination of adsorption phenomena within mesoporous solids.

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Hierarchical porous catalysts offer highly connected architectures for enhanced transport of bulky molecules and the sustainable manufacturing of bio-derived platform chemicals and fuels.

Materials characterisationNitrogen porosimetry was undertaken on a Quantachrome Autosorb IQTPX porosimeter with analysis using ASiQwin v3.01 software. Samples were degassed at 150ºC for 12 h before recording N2 adsorption/desorption isotherms. BET surface areas were calculated over the relative pressure range 0.02-0.2. Mesopore properties were calculated applying the BJH (Barrett-Joyner-Halenda) method to the desorption isotherm for relative pressures >0.35, and fitting of isotherms to the relevant DFT (density functional theory) kernel within the software package. Powder X-ray diffraction patterns were recorded using a Bruker D8 diffractometer employing a Cu K (1.54 Å) source fitted with a Lynx eye high-speed strip detector. Low-angle patterns were recorded for 2θ = 0.3-8º with a step size of 0.01º. Wide-angle patterns were recorded for 2θ = 10-80º with a step size of 0.02º. XPS spectra were recorded using a Kratos Axis HSi spectrometer fitted with an Al kα (1486.6 eV) monochromated source and a charge neutraliser. High resolution spectra were run with a pass energy of 40. All spectra were calibrated to adventitious carbon (284.8 eV). Peak fitting was performed using CASAv2.3.18PR1.0. All peaks were fit with a Shirley background and a GL(30) lineshape. Thermogravimetric analysis was conducted using a Mettler-Toledo TGA/DSC 2 STAR* system at 10 ºC min -1 under flowing N2/O2 (80:20 v/v 20 cm 3 min -1 ) fitted with a Pfeiffer ThermoStar mass spectrometer. CO2 titrations were performed using a Quantachrome ChemBET 3000. Samples were outgassed at 400 ºC under flowing helium (20 cm 3 min -1 ) for 1 hour prior to analysis. Transmission electron microscopy (TEM) imaging was performed using a JEOL 2100F FEG TEM with a Schottky field-emission source, equipped with an Oxford INCAx-sight Si(Li) detector for energy-dispersive spectroscopy (EDX). High-resolution (scanning) transmission electron microscopy (S)TEM images were recorded on either a FEI Tecnai F20 FEG TEM operating at 200 kV equipped with an

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The utility of carbon materials in applications as diverse as drug delivery and photocatalysis is often undermined by the complexity of their surface chemistry; different sources of carbon give rise to a varied mixture of functional groups and hence different properties. Considerable efforts have been made to identify specific groups at these surfaces and elucidate the complex interactions that take place but even on materials such as graphene and carbon nanotubes there remains uncertainty about the nature of the components present and their role in the nucleation of other functional materials at the surface. The present study uses highly ordered pyrolytic graphite (HOPG) as a model on which the fundamental properties of specific functional groups and their interactions with deposited nanoparticles can be characterised. We have shown that treatment of HOPG surfaces with low concentrations of hydrochloric acid results in significant topographic changes to the surface and a low concentration of oxygen containing species. From selective derivatization and a comparison of their XP spectra, the latter can be unambiguously identified as surface hydroxyls. DFT calculations have shown that these groups are stable in close proximity to each other. Heating to 573 K leads to conversion of the hydroxyls to mixture of two states, one of which is identified as a ketone whilst the other is proposed to be an ether. Gold deposition on the surface from aqueous solutions of chloroauric acid is shown to be strongly influenced by the nature of the oxygen species present.

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The relative surface affinities of pyridine within microporous HZSM-5 zeolites are explored using two-dimensional 1H nuclear magnetic resonance (NMR) relaxation time measurements. The dimensionless ratio of longitudinal-to-transverse nuclear spin relaxation...