Playing with covalent triazine framework tiles for improved CO2 adsorption properties and catalytic performance.

The rational design and synthesis of covalent triazine frameworks (CTFs) from defined dicyano-aryl building blocks or their binary mixtures is of fundamental importance for a judicious tuning of the chemico-physical and morphological properties of this class of porous organic polymers. In fact, their gas adsorption capacity and their performance in a variety of catalytic transformations can be modulated through an appropriate selection of the building blocks. In this contribution, a set of five CTFs (CTF1-5) have been prepared under classical ionothermal conditions from single dicyano-aryl or heteroaryl systems. The as-prepared samples are highly micro-mesoporous and thermally stable materials featuring high specific surface area (up to 1860 m2·g-1) and N content (up to 29.1 wt %). All these features make them highly attractive samples for carbon capture and sequestration (CCS) applications. Indeed, selected polymers from this series rank among the CTFs with the highest CO2 uptake at ambient pressure reported so far in the literature (up to 5.23 and 3.83 mmol·g-1 at 273 and 298 K, respectively). Moreover, following our recent achievements in the field of steam- and oxygen-free dehydrogenation catalysis using CTFs as metal-free catalysts, the new samples with highest N contents have been scrutinized in the process to provide additional insights to their complex structure-activity relationship.

Design and Fabrication of Highly Reducible PtCo Particles Supported on Graphene-Coated ZnO.

Cobalt particles dispersed on an oxide support form the basis of many important heterogeneous catalysts. Strong interactions between cobalt and the support may lead to irreducible cobalt oxide formation, which is detrimental for the catalytic performance. Therefore, several strategies have been proposed to enhance cobalt reducibility, such as alloying with Pt or utilization of nonoxide supports. In this work, we fabricate bimetallic PtCo supported on graphene-coated ZnO with enhanced cobalt reducibility. By employing a model/planar catalyst formulation, we show that the surface reduction of cobalt oxide is substantially enhanced by the presence of the graphene support as compared to bare ZnO. Stimulated by these findings, we synthesized a realistic powder catalyst consisting of PtCo particles grafted on graphene-coated ZnO support. We found that the addition of graphene coating enhances the surface reducibility of cobalt, fully supporting the results obtained on the model system. Our study demonstrates that realistic catalysts with designed properties can be developed on the basis of insights gained from model catalytic formulation.

Colloid Approach to the Sustainable Top-Down Synthesis of Layered Materials.

The successful future of 2D materials, which are crucial for accelerating technology development and societal requirements, depends on their efficient preparation in an economical and ecological way. Herein, we present a significant advance in the top-down exfoliation and dispersion method via an aqua colloid approach. We demonstrate that a broad family of natural oil-in-water emulsification agents with an elevated hydrophilic/lipophilic balance acts in the exfoliation of layered materials and the formation of their concentrated colloids. The concentration exceeds 45 g/L for exfoliated few-layered graphene sheets possessing a micrometer size. The exfoliation of carbon nanofibers provides one of the best known unsupported and N-undoped metal-free catalysts to date in the selective dehydrogenation of ethylbenzene to styrene. Other examples include aqua colloids of exfoliated/dispersed nitrides, carbides, or nanodiamonds.

Aziridine-Functionalized Multiwalled Carbon Nanotubes: Robust and Versatile Catalysts for the Oxygen Reduction Reaction and Knoevenagel Condensation.

This paper describes the exohedral N-decoration of multiwalled carbon nanotubes (MWCNTs) with NH-aziridine groups via [2 + 1] cycloaddition of a tert-butyl-oxycarbonyl nitrene followed by controlled thermal decomposition of the cyclization product. The chemical grafting with N-containing groups deeply modifies the properties of the starting MWCNTs, generating new surface microenvironments with specific base (Brønsted) and electronic properties. Both of these features translate into a highly versatile single-phase heterogeneous catalyst (MW@NAz) with remarkable chemical and electrochemical performance. Its surface base character promotes the Knoevenagel condensation with activity superior to that of related state of the art N-doped and N-decorated carbon nanomaterials; the N-induced electronic surface redistribution drives the generation of high-energy surface "C" sites suitable for O2 activation and its subsequent electrochemical reduction (ORR).

A highly N-doped carbon phase "dressing" of macroscopic supports for catalytic applications.

The straightforward "dressing" of macroscopically shaped supports (i.e.ß-SiC and α-Al2O3) with a mesoporous and highly nitrogen-doped carbon-phase starting from food-processing raw materials is described. The as-prepared composites serve as highly efficient and selective metal-free catalysts for promoting industrial key-processes at the heart of renewable energy technology and environmental protection.

Activation of few layer graphene by µW-assisted oxidation in water via formation of nanoballs - Support for platinum nanoparticles.

The functionalization of carbon nanomaterials in controlled and selective manner and in order to stabilize small metal nanoparticles is of high interest particularly in the catalysis field. We present the µ-waves assisted few layer graphene (FLG) oxidation in water, which results in a partial sheets exfoliation and formation of oxygen functionalized carbon nanoballs, supported on highly graphitized graphene sheets. This double morphology material allows homogenous anchoring of Pt nanoparticles, while the advantages of planar and highly crystallized FLG are preserved. For comparison, acid treated FLG (conventional heating) exhibits highly hydrophobic and inert surface with carboxylic groups as anchoring sides localized at the FLG edges. Despite similar oxygen content, the performed physicochemical analyses depict different nature and localization of the oxygen/defects functionalities introduced in water (in µ-waves) and acid treated FLGs. Finally, the addition of FLG during the preparation of Pt particles-carried out by µ-wave assisted polyol method yields small nanoparticles with average size of 1nm.