“Red Carbon”: A Rediscovered Covalent Crystalline Semiconductor

Abstract

Carbon suboxide (C3O2) is a unique molecule able to polymerize spontaneously into highly conjugated light‐absorbing structures at temperatures as low as 0 °C. Despite obvious advantages, little is known about the nature and the functional properties of this carbonaceous material. In this work, the aim is to bring “red carbon,” a forgotten polymeric semiconductor, back to the community's attention. A solution polymerization process is adapted to simplify the synthesis and control the structure. This allows one to obtain this crystalline covalent material at low temperatures. Both spectroscopic and elemental analyses support the chemical structure represented as conjugated ladder polypyrone ribbons. Density functional theory calculations suggest a crystalline structure of AB stacks of polypyrone ribbons and identify the material as a direct bandgap semiconductor with a medium bandgap that is further confirmed by optical analysis. The material shows promising photocatalytic performance using blue light. Moreover, the simple condensation–aromatization route described here allows the straightforward fabrication of conjugated ladder polymers and can be inspiring for the synthesis of carbonaceous materials at low temperatures in general.

Red Carbon Mediated Formation of Cu2O Clusters Dispersed on the Oxocarbon Framework by Fehling's Route and their Use for the Nitrate Electroreduction in Acidic Conditions

“…The initial step involved creating a red carbon oligomeric matrix with homogenously dispersed copper ions, providing the foundational structure for subsequent thermal treatments. For that, we adapted the solution-based approach recently introduced by Odziomek et al [41] Malonic acid dehydrates upon heating in acetic anhydride forming C 3 O 2 which spontaneously polymerizes into highly conjugated red carbon oligomers. To introduce Cu ions, CuSO 4 was added to the initial mixture of malonic acid and acetic anhydride, thus the polymerization of carbon suboxide occurred in the presence of Cu ions.…”

“…Except for the possible stronger interaction with Cu species, the enhanced cross-linking of carbonous framework after 400 °C also resulted in the increase amount of C═C bond, leading to the higher conjugation effect, thus the decrease of bond order of C═O. Further-more, the sharp peak at 800 cm −1 , corresponding to the collective vibrations of adjacent ether oxygens of the red carbon, [41,44] decreased in the samples of pCO-Cu3 and pCO-Cu4, indicating the elimination of these oxygen groups (Figure 2b). XRD analysis also served to monitor the carbonaceous network's evolution.…”

Tin (II) Chloride Salt Melts as Non‐Innocent Solvents for the Synthesis of Low‐Temperature Nanoporous Oxo‐Carbons for Nitrate Electrochemical Hydrogenation

“…This conjugated planar structure and the absence of structure terminating and inactive C─H bonds are attractive for synthesizing carbonaceous materials at milder conditions. [21,29] In order to minimize the temperature required for thermal condensation and the formation of a rigid, more organized carbon network, RC was thermally treated in SnCl 2 /KCl salt melt (SnK) as its melting point is lower than the onset of RC decomposition and cross-linking (Figure S1, Supporting Information). In addition, Sn(II) can act as both Lewis acid and base providing specific interaction between the p-block metal and the oxygen atoms in RC.…”

“…Red carbon (RC), an oligomer of chemical composition (C 3 O 2 ) n , was selected as the model carbon precursor. [ 21 ] The high affinity of tin for oxygen and its ability to undergo redox reaction from 2+ to 4+, cause a remarkable effect on the condensation‐aromatization process and porosity development. Already at 300 °C, a highly porous oxocarbon structure (658 m 2 g −1 ) emerged, reaching a value of 1600 m 2 g −1 at 400 °C, which was stable at least to 800 °C.…”

Rational design of a carbon/potassium poly(heptazine imide) heterojunction for enhanced photocatalytic H2 and H2O2 evolution

“…15 In general, carbonaceous materials (CMs) in photocatalysis can serve as modiers on the surface of semiconductors or as photosensitizers themselves. [16][17][18][19][20] Recent advances have demonstrated that p-conjugated bonding between g-C 3 N 4 and CMs (e.g., graphene, carbon dots and carbon nanotubes) can create an intimate electronic contact and promote charge transport from the light transducer to the carbon surface, thus preventing carrier recombination. [21][22][23] CMs can also extend the light absorption and take on the role of a photosensitizer.…”