Origin of microporosity in chalcogen-doped carbon materials: The case of selenium-doped carbogels

The outstanding properties of carbon materials doped with p-block elements are usually attributed directly to the presence of certain foreign atoms. By using the example of selenium-doped carbon gels, we hereby postulate that in many cases the properties of doped carbon materials are not determined by the presence of the heteroatom itself, but rather by how the element affects the carbon structure during high-temperature synthesis. Se-doped microporous carbogels were obtained via sol-gel polycondensation of resorcinol and 2-formylselenophene followed by pyrolysis at 600–1200 °C. Pyrolysis temperatures above 800 °C result in a decrease in the Se-content accompanied by a distinct increase in ultramicroporosity. A comparative analysis of oxygen-, sulfur- and selenium-doped carbogels shows that chalcogens increase the porosity of carbonaceous materials via the high-temperature oxidation of carbon to corresponding dichalcogenides (CO2, CS2 or CSe2), but their oxidative power diminishes with increasing atomic mass. Consequently, S and Se are more selective carbon oxidants.