Tuning molecular adsorption in SBA-15-type periodic mesoporous organosilicas by systematic variation of their surface polarity

Moon, Hee‐Jong; Han, Songi; Scott, Susannah L.

doi:10.1039/d0sc00168f

Cited by 13 publications

(21 citation statements)

References 58 publications

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“…In general, mesostructured silicas are synthesized from the mixture of a silicon source and a structuring agent that confers an organized mesoporous structure, high surface area, and tunable pore size as well as a heterogeneous surface composed of both hydrophobic sites—siloxane groups, and polar sites—silanol groups. 9 − 11 Some arguments against the use of this type of inorganic template material are related to the production cost and scalability. 9 − 12 In this sense, production optimization and lower cost techniques have been explored, including use of alternative silicon sources such as rice husk 13 , 14 or coal fly ash 15 and washing methods with environmentally friendly solvents to remove the template.…”

Section: Introductionmentioning

confidence: 99%

“…The discovery of mesostructured silicas led to the opening of a new field of research in the design of porous solids. In general, mesostructured silicas are synthesized from the mixture of a silicon source and a structuring agent that confers an organized mesoporous structure, high surface area, and tunable pore size as well as a heterogeneous surface composed of both hydrophobic sitessiloxane groups, and polar sitessilanol groups. − Some arguments against the use of this type of inorganic template material are related to the production cost and scalability. − In this sense, production optimization and lower cost techniques have been explored, including use of alternative silicon sources such as rice husk , or coal fly ash and washing methods with environmentally friendly solvents to remove the template . Additionally, the ability of SBA-15 to host a large series of functional groups by methods of cocondensation, isomorphic replacement, or grafting leads it to be a promising porous solid that opens a tremendously valuable possibility of developing solids with very specific characteristics, for industrial applications related to adsorption processes , and membrane separation, , in pharmaceutical applications like drug delivery, , biosensing, , and for catalysis. , …”

Section: Introductionmentioning

confidence: 99%

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Enthalpies of Immersion in Caffeine and Glyphosate Aqueous Solutions of SBA-15 and Amino-Functionalized SBA-15

et al. 2021

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Mesostructured silica SBA-15 and amino-functionalized silica SBA-15-NH 2 were synthesized, and then, characterization, adsorption capacity, and immersion enthalpies in caffeine and glyphosate on SBA-15 and SBA-15-NH 2 were evaluated. The enthalpy parameter was determined using a local construction Tian-type heat conduction calorimeter. Calorimetric studies in caffeine solutions exhibit negative enthalpy values; exothermic process characteristics for SBA-15 were between −13.90 and −194.06 J g –1 and those for SBA-15-NH 2 were between −7.22 and −60.34 J g –1 , and the adsorption capacity of caffeine was better in SBA-15 than that in SBA-15-NH 2 . In contrast, the enthalpies of immersion in glyphosate solutions were −5.06 to −56.2 J g –1 and the immersion of SBA-15-NH 2 in each solution generated enthalpy values of −9.06 to −41.2 J g –1 , but the adsorption capacity of glyphosate was better in the amino-functionalized SBA-15. The results show that functionalization of SBA-15 produced differences in physicochemical characteristics of solids, since energy and affinity for the calorimetric liquids are related to the surface properties of solids as well as the chemical nature of the target molecule, immersion enthalpy, was different.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enthalpies of Immersion in Caffeine and Glyphosate Aqueous Solutions of SBA-15 and Amino-Functionalized SBA-15

et al. 2021

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“…The fluorescence from a solvatochromic dye molecule, such as Prodan, is an indirect probe of hydrophobicity. The emission energy reflects the local polarity, , which is closely related to hydrophobicity. − The emission of adsorbed Prodan has been used as an empirical measure of relative average hydrophobicity in a series of mesoporous organosilicas. , Overhauser Dynamic Nuclear Polarization (ODNP) relaxometry of interfacial water provides another indirect measure of surface hydrophobicity. ODNP relies on cross-relaxation due to dipolar coupling between the 1 H nuclear spin of a water molecule and the unpaired electron spin of a nearby radical (a.k.a.…”

Section: Introductionmentioning

confidence: 99%

Evidence for Entropically Controlled Interfacial Hydration in Mesoporous Organosilicas

et al. 2022

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At aqueous interfaces, the distribution and dynamics of adsorbates are modulated by the behavior of interfacial water. Hydration of a hydrophobic surface can store entropy via the ordering of interfacial water, which contributes to the Gibbs energy of solute binding. However, there is little experimental evidence for the existence of such entropic reservoirs, and virtually no precedent for their rational design in systems involving extended interfaces. In this study, two series of mesoporous silicas were modified in distinct ways: (1) progressively deeper thermal dehydroxylation, via condensation of surface silanols, and (2) increasing incorporation of nonpolar organic linkers into the silica framework. Both approaches result in decreasing average surface polarity, manifested in a blue-shift in the fluorescence of an adsorbed dye. For the inorganic silicas, hydrogen-bonding of water becomes less extensive as the number of surface silanols decreases. Overhauser dynamic nuclear polarization (ODNP) relaxometry indicates enhanced surface water diffusivity, reflecting a loss of enthalpic hydration. In contrast, organosilicas show a monotonic decrease in surface water diffusivity with decreasing polarity, reflecting enhanced hydrophobic hydration. Molecular dynamics simulations predict increased tetrahedrality of interfacial water for the organosilicas, implying increased ordering near the nm-size organic domains (relative to inorganic silicas, which necessarily lack such domains). These findings validate the prediction that hydrophobic hydration at interfaces is controlled by the microscopic length scale of the hydrophobic regions. They further suggest that the hydration thermodynamics of structurally heterogeneous silica surfaces can be tuned to promote adsorption, which in turn tunes the selectivity in catalytic reactions.

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“…The Bluemel group pioneered in a series of seminal papers the application of CPMAS, in general and in particular, of HRMAS (high-resolution magic-angle spinning [ 115 ]), a solid-state NMR experiment, which employs the partial motional averaging of anisotropies for the investigation of physisorbed or chemisorbed molecules on surfaces, the characterization of novel porous catalysts [ 104 , 105 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 ]. Important contributions by the Coperet group were studies of various supported organometallic catalysts by SSNMR (see [ 86 , 87 , 90 , 92 , 126 , 127 , 128 , 129 , 130 , 131 , 132 ]) and by the Scott group [ 133 , 134 , 135 , 136 , 137 , 138 ], who developed a series of novel porous catalytic materials and investigated in detail the factors determining their adsorption and reactivity properties and by the Pruski [ 69 , 70 , 71 , 72 , 139 , 140 , 141 , 142 , 143 , 144 , 145 ] and Buntkowsky [ 146 , 147 , 148 , 149 , 150...…”

Section: Introductionmentioning

confidence: 99%

Small Molecules, Non-Covalent Interactions, and Confinement

Buntkowsky

Vogel

2020

Molecules

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This review gives an overview of current trends in the investigation of small guest molecules, confined in neat and functionalized mesoporous silica materials by a combination of solid-state NMR and relaxometry with other physico-chemical techniques. The reported guest molecules are water, small alcohols, and carbonic acids, small aromatic and heteroaromatic molecules, ionic liquids, and surfactants. They are taken as characteristic role-models, which are representatives for the typical classes of organic molecules. It is shown that this combination delivers unique insights into the structure, arrangement, dynamics, guest-host interactions, and the binding sites in these confined systems, and is probably the most powerful analytical technique to probe these systems.

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Tuning molecular adsorption in SBA-15-type periodic mesoporous organosilicas by systematic variation of their surface polarity

Abstract: Adsorption of organic molecules from solution into mesoporous organosilicas is modulated by the relative polarity of the surface.

Cited by 13 publications

References 58 publications

Enthalpies of Immersion in Caffeine and Glyphosate Aqueous Solutions of SBA-15 and Amino-Functionalized SBA-15

Enthalpies of Immersion in Caffeine and Glyphosate Aqueous Solutions of SBA-15 and Amino-Functionalized SBA-15

Evidence for Entropically Controlled Interfacial Hydration in Mesoporous Organosilicas

Small Molecules, Non-Covalent Interactions, and Confinement

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