Charge transport in polymeric graphitic carbon nitrides is shown to proceed via diffusive hopping of electron and hole polarons with reasonably high mobilities >10(-5) cm(2) V(-1) s(-1). The power-law behavior of the ultrafast luminescence decay exhibits that the predominant transport direction is perpendicular to the graphitic polymer sheets, thus complementing 2D materials like graphene.

Mesoporous carbon nitrides, silicas and their composites have been prepared by a combined sol-gel and thermal condensation approach. Precursors for the carbon nitride (cyanamide) and silica (TEOS) are mixed and condensed simultaneously. After condensation and heat treatment it is observed that the carbon nitride and silica formed highly interpenetrating mesophases which leads either to the formation of mesoporous carbon nitride or silica after selective removal of one of the phases. Importantly, the carbon nitride preserves its graphitic stacking even in the spatial confinement introduced by the surrounding silica phase. As both precursors are liquids this approach allows convenient shaping into thin and thick films or monoliths of mesoporous carbon nitrides. Enhanced photocatalytic activity is observed for the production of hydrogen from water when these mesoporous carbon nitrides are applied as photocatalyst in comparison to the bulk, but also to other mesoporous carbon nitrides, prepared by the reported two-step, hard templating approach.

Herein, we present an approach to create a hybrid between single-atom-dispersed silver and a carbon nitride polymer. Silver tricyanomethanide (AgTCM) is used as a reactive comonomer during templated carbon nitride synthesis to introduce both negative charges and silver atoms/ions to the system. The successful introduction of the extra electron density under the formation of a delocalized joint electronic system is proven by photoluminescence measurements, X-ray photoelectron spectroscopy investigations, and measurements of surface ζ-potential. At the same time, the principal structure of the carbon nitride network is not disturbed, as shown by solid-state nuclear magnetic resonance spectroscopy and electrochemical impedance spectroscopy analysis. The synthesis also results in an improvement of the visible light absorption and the development of higher surface area in the final products. The atom-dispersed AgTCM-doped carbon nitride shows an enhanced performance in the selective hydrogenation of alkynes in comparison with the performance of other conventional Ag-based materials prepared by spray deposition and impregnation-reduction methods, here exemplified with 1-hexyne.

The base catalytic properties of a series of triazine-based covalent organic frameworks were evaluated for the conversion of CO₂ to organic carbonates. The high number of basic nitrogen sites of the as-synthesized frameworks efficiently catalyzed the formation of cyclic carbonates via the cycloaddition of CO₂ to different starting epoxides. The structural and chemical tunability of the covalent triazine frameworks allowed the fine evaluation of key parameters influencing the observed catalytic activities. An increased surface area and presence of additional mesopores dramatically enhance the activity of the investigated catalytic materials. The chemical composition was also found to influence the reaction, as evidenced by an increased activity at lower reaction temperatures, when a more basic, pyridine-based, framework was used as catalyst. Finally, the activity in the two-step cycloaddition/transesterification catalysis of dimethyl carbonate was evaluated in a one-batch process.

Supported cobalt oxide nanoparticles (NPs) have been prepared by wetness impregnation on different supports and subsequent heat treatment in argon at 350 °C for 2 h. The thus prepared cobalt oxide (Co3O4) can be well dispersed on carbonaceous materials such as activated carbon (AC) and covalent trizaine frameworks (CTF), with average particle sizes below 5 nm. The catalytic performance of supported Co3O4 NPs was tested by aerobic oxidation of alcohols in liquid phase. The results show that AC supported Co3O4 NPs, Co3O4/AC, exhibit ∼100% conversions for alcohol oxidation and can be reused for at least 4 runs without appreciable loss of activity, when a thermal regeneration step is carried out, suggesting that the Co3O4 NPs are well embedded and stabilized on the support, making Co3O4/AC a promising catalyst for aerobic oxidation of alcohols in liquid phase.

Two emerging material classes are combined in this work, namely polymeric carbon nitrides and microporous polymer networks. The former, polymeric carbon nitrides, are composed of amine-bridged heptazine moieties and showed interesting performance as a metal-free photocatalyst. These materials have, however, to be prepared at high temperatures, making control of their chemical structure difficult. The latter, microporous polymer networks have received increasing interest due to their high surface area, giving rise to interesting applications in gas storage or catalysis. Here, the central building block of carbon nitrides, a functionalized heptazine as monomer, and tecton are used to create microporous polymer networks. The resulting heptazine-based microporous polymers show high porosity, while their chemical structure resembles the ones of carbon nitrides. The polymers show activity for the photocatalytic production of hydrogen from water, even under visible light illumination.

Sensing mechanism illustrating proton hopping between the water molecules physisorbed on the COF-TXDBA surface.

The nature of a nickel-based co-catalyst deposited on a sol-gel prepared porous graphitic-carbon nitride (sg-CN), for photocatalytic H 2 production from water, has been investigated. The formation of the active catalytic species, charge separation and recombination of the photogenerated electrons and holes during photochemical H 2 evolution has been determined for the first time using in situ EPR spectroscopy.