The Molecular Design of Active Sites in Nanoporous Materials for Sustainable Catalysis

Abstract

At the forefront of global development, the chemical industry is being confronted by a growing demand for products and services, but also the need to provide these in a manner that is sustainable in the long-term. In facing this challenge, the industry is being revolutionised by advances in catalysis that allow chemical transformations to be performed in a more efficient and economical manner. To this end, molecular design, facilitated by detailed theoretical and empirical studies, has played a pivotal role in creating highly-active and selective heterogeneous catalysts. In this review, the industrially-relevant Beckmann rearrangement is presented as an exemplar of how judicious characterisation and ab initio experiments can be used to understand and optimise nanoporous materials for sustainable catalysis.

Butane Isomerization as a Diagnostic Tool in the Rational Design of Solid Acid Catalysts

“…The interest in zeolites derives from the ability to isomorphously substitute framework Si 4+ sites with Al 3+ , creating a "net negative charge". This negative charge is then neutralized by a proton, associated with the framework, creating a BAS, hence their use as solid-acid catalysts [42]. This leads to protonated zeolites having the formula:…”

“…By comparing reaction profiles for frameworks with similar acid site quantities, the reaction order with respect to n-butane could inform investigators of how sparse or clustered the acid sites are, providing the acid strength of the materials is similar. By extending this to the myriad of dopants that are available for isomorphous substitution into aluminophosphate systems, this may serve to verify computational predictions of whether dopants substitute via an atomically clustered or distributed model [42,72,73].…”

Effect of Zeolitic Hydroxyl Nests on the Acidity and Propane Aromatization Performance of Zinc Nitrate Impregnation-Modified HZSM-5 Zeolite

“…9−16 So far, our knowledge about the zeolitic hydroxyl nests has been mainly limited to defective S-1 zeolites. Defective S-1 zeolite has been investigated since the 1990s mainly because that it is a kind of mildly acidified catalytic material, showing high efficiency and selectivity in the gas-phase Beckman rearrangement of cyclohexanoneoxime, 17,18 and that with various density of defects, it can be conveniently obtained by hydrothermal synthesis in basic media. 2 Concerning the hydroxyl nests of defective S-1 zeolite, the following points are worth mentioning.…”

“…Although some studies have been done, little is truly understood about the tender acidity and unique catalytic performance 17,18 of defective S-1 zeolite due mainly to the weakness of the acidity of defective S-1 zeolite. 1,6−8 HZSM-5 zeolite is a highly acidic catalytic material, which has been widely used as a catalyst in many heterogeneous catalytic processes.…”

Surface Heterogeneous Nucleation-Mediated Release of Beta-Carotene from Porous Silicon

“…The possibilities to finely tune their physico-chemical properties, often by simple modification of their synthesis, make nanoporous materials extremely flexible platforms to realize advanced materials with well-controlled and tunable characteristics. Porous materials are highly investigated for applications ranging from catalysis [ 1 , 2 , 3 , 4 ], via energetics [ 5 , 6 , 7 ], to biology [ 8 , 9 , 10 , 11 ]. Often the specific properties are due to the way the nanostructuring affects the interactions between the porous scaffold and the substances it comes in to contact with.…”