Nitrogen-containing porous carbon materials by twin polymerization

Significance 

The recent technological evolution has enabled researchers establish that the incorporation of hetero atoms into carbon materials have potential to influence the carbon structure by adding sp2 defects. Specifically, it has already been shown that nitrogen-doped carbon materials possess, for instance, a different electrochemical behavior than the respective original carbon species. Further studies have unveiled that the stabilization of metal nanoparticles with donating nitrogen surface functionalities can be enhanced upon addition of different nitrogen sources. Consequently, this opens doors for a wide variety of applications such as CO2 capturing. Several approaches can be used to incorporate nitrogen into carbon matrix. One of these approaches is twin polymerization. Using this technique, sulfur- or boron-doped carbon materials can be obtained by modification of the organic moieties in order to obtain sulfur- or boron-doped carbon materials. Unfortunately, there is not a direct synthetic technique for doping porous carbon materials with nitrogen by twin polymerization at present.

To this note, a team of researchers led by Professor Heinrich Lang at Chemnitz University of Technology synthesized new specific type of pyrrole-based twin monomers. They studied monomers’ polymerization/copolymerization behavior as well as their use for the generation of nitrogen-doped, highly porous carbon materials. Their work is currently published in the research journal, Colloid and Polymer Science.

In brief, the research method employed commenced with the preparation of the twin monomers by reacting specific alcohols with silicon tetrachloride at a specific molar ratio in the presence of triethylamine. Next, the as-prepared twin monomers Si(OCH2cC4H3NR)4 (5, R = Me; 6, R = H) were characterized by Nuclear magnetic resonance and Infrared radiation spectroscopy, ESI mass spectrometry, and microanalysis. The researchers then investigated the thermal behavior of 5 and 6 by differential scanning calorimetry. Additionally, the twin polymerization behavior of 5 and 6 was further assessed under acidic and thermal initiation, respectively. Further investigation using other techniques was also carried out.

The authors observed a different substitution pattern in the hybrid materials obtained by the twin polymerization of 6. In addition, the nitrogen content of the obtained hybrid materials was determined by microanalysis revealing higher nitrogen contents in the hybrid material obtained from 6. Moreover, while the thermal product exhibited a higher microporous part, the acid-initiated material was seen to be more mesoporous. The researchers also noted that the nitrogen content of the porous carbon materials only slightly decreased during carbonization.

In summary, the German study presented a straightforward synthetic methodology for doping porous carbon materials with nitrogen by twin polymerization. In general, the results they obtained were supported by HAADF-STEM studies, that showed the typical micro-structuring of a twin polymer. Altogether, they concluded that, mostly pyrrolic nitrogen along with pyridinic nitrogen moieties can be found within the carbon materials such as the monomers 5 and 6 investigated in this case.

Reference

Christian Schliebe, Julian Noll, Sebastian Scharf, Thomas Gemming, Andreas Seifert, Stefan Spange, Daniel Lehmann, Dietrich R. T. Zahn, Benjamin Fiedler, Joachim Friedrich, Thomas Blaudeck, Heinrich Lang. Nitrogen-containing porous carbon materials by twin polymerization. Colloid and Polymer Science (2018) volume 296, page 413–426.

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