Positive and negative regulation of carbon nanotube catalysts through encapsulation within macrocycles

Abstract

One of the most attractive applications of carbon nanomaterials is as catalysts, due to their extreme surface-to-volume ratio. The substitution of C with heteroatoms (typically B and N as p- and n-dopants) has been explored to enhance their catalytic activity. Here we show that encapsulation within weakly doping macrocycles can be used to modify the catalytic properties of the nanotubes towards the reduction of nitroarenes, either enhancing it (n-doping) or slowing it down (p-doping). This artificial regulation strategy presents a unique combination of features found in the natural regulation of enzymes: binding of the effectors (the macrocycles) is noncovalent, yet stable thanks to the mechanical link, and their effect is remote, but not allosteric, since it does not affect the structure of the active site. By careful design of the macrocycles’ structure, we expect that this strategy will contribute to overcome the major hurdles in SWNT-based catalysts: activity, aggregation, and specificity.

The Supramolecular Chemistry of Strained Carbon Nanohoops

“…Pérez and co‐workers have recently developed a concept for synthesizing mechanically interlocked carbon nanotubes (“ MINTs ”) which is based on “clipping” rings around single‐walled carbon nanotubes ( SWCNTs ) and represents an appealing approach for functionalizing and solution‐processing of these nanomaterials. Ohe and co‐workers have reported a related “ring‐toss” approach, which relies on the spontaneous interaction of π‐conjugated carbon nanohoops (π‐extended derivatives of [8]CPPA , [9]CPPA , and [10]CPPA ) with SWCNTs , which is why the resulting materials are perhaps best described as poly‐pseudorotaxanes .…”

Combined high degree of carboxylation and electronic conduction in graphene acid sets new limits for metal free catalysis in alcohol oxidation

“…This mechanism was later conrmed by theory and experiments. 37 Obviously, this mechanism cannot be applied with an insulating material acting as a catalyst, thus justifying the negligible activity shown by GO. Therefore, the key to the superior catalytic activity of GA is not simply related to the presence of carboxyl groups, which are known to be oxygen activators, 38,39 but to the fact that these catalytically active centers are electronically connected to a reduced carbon scaffold that can be used as an electron reservoir/sink.…”

Supramolekulare Chemie von gespannten Kohlenstoffnanoreifen

“…Pérez et al. haben ein Konzept zur Synthese von mechanisch verzahnten Kohlenstoff‐Nanoröhren (mechanically interlocked carbon nanotubes, MINTs) entwickelt, bei dem Ringe um einwandige Kohlenstoff‐Nanoröhren (SWCNTs) zuschnappen (Clipping) und so einen attraktiven Ansatz zur Funktionalisierung dieser Nanomaterialien und deren Bearbeitung in Lösung bieten. Ohe und Mitarbeiter haben einen “Ringe werfen”‐Ansatz entwickelt, bei dem die spontane Wechselwirkung von π‐konjugierten Kohlenstoff‐Nanoreifen (π‐vergrößerte Derivate von [8]CPPA , [9]CPPA und [10]CPPA ) und SWCNTs genutzt wird, wodurch die resultierenden Materialien am besten als Poly‐Pseudorotaxane beschrieben werden können .…”