Bottom-up synthesis of pyridinic nitrogen-doped carbon materials from brominated two-fused-ring aromatics at low carbonization temperatures

抄録

Pyridinic nitrogen-containing carbon materials are expected to have excellent performance as electrodes and catalysts. Carbon materials containing only pyridinic nitrogen have been synthesized in recent years, and the use of two-fused-ring aromatic compounds as precursors enabled the synthesis of relatively inexpensive pyridinic nitrogen-containing carbon materials. However, a two-fused-ring aromatic compound such as isoquinoline (IQ) required a relatively high temperature (973 K) for carbonization, causing C–N bond cleavage, and the percentage of pyridinic nitrogen was relatively low: 52% of the N atoms are pyridinic. This study synthesized pyridinic nitrogen-containing carbon materials from six brominated IQs. The bromination of IQs lowered the carbonization temperatures to 673–873 K, which helped avoid the decomposition of the pyridinic nitrogen. Among these six precursors, the one with two bromine substitutions (1,4-dibromoisoquinoline) had the highest percentage of pyridinic nitrogen (65%) at 773 K. The factors that increase the percentage of pyridinic nitrogen are (1) avoiding the formation of a 1,10-phenanthroline-like structure during dimerization, (2) avoiding the formation of N–H and promoting the scission of the formed C–N in dimers formed after C=C coupling at bromine-substituted positions between precursors, and (3) forming a more ordered six-membered ring structure by the introduction of two or more highly reactive bromines.