Mechanochemical bottom-up synthesis of phosphorus-linked, heptazine-based carbon nitrides using sodium phosphide

Abstract

Herein, we present the bottom-up, mechanochemical synthesis of phosphorus-bridged heptazine-based carbon nitrides (g-h-PCN). The structure of these materials was determined through a combination of powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), 31P magic angle spinning nuclear magnetic resonance (MAS NMR), density functional theory (DFT) and electron energy loss spectroscopy (EELS). Compared to traditional furnace-based techniques, the presented method utilizes milder conditions, as well as shorter reaction times. Both samples of g-h-PCN directly after milling and aging and after an hour of annealing at 300 °C (g-h-PCN300) show a reduction in photoluminescent recombination, as well as a nearly two-time increase in photocurrent under broad spectrum irradiation, which are appealing properties for photocatalysis.

Dissecting Mechanochemistry III

“…Moreover, Štrbac and Margetić used dibrominated polycyclic imides as substrates to generate reactive alkenes, which could be trapped in situ by several dienes through Diels−Alder cycloadditions by ball milling (Scheme 3) [7]. Further, Moores and co-workers synthesized phosphorusbridged heptazine-based carbon nitrides (g-h-PCN) from an initial mechanical treatment of trichloroheptazine and Na 3 P, once again highlighting the importance of halogenated organic molecules as building blocks for graphitic heptazine materials (Scheme 4) [8]. Another halogenated molecule, 2,3-dichloro-5,6-dicyano-1,4benzoquinone (DDQ), proved to be an appropriate oxidant for C-N couplings towards the synthesis of 1,2-disubstituted benzimidazoles and quinazolin-4(3H)-one derivatives under mechanochemical conditions, as evidenced by Mal and co-workers (Scheme 5) [9].…”

“…Further, Moores and co-workers synthesized phosphorus-bridged heptazine-based carbon nitrides (g-h-PCN) from an initial mechanical treatment of trichloroheptazine and Na 3 P, once again highlighting the importance of halogenated organic molecules as building blocks for graphitic heptazine materials ( Scheme 4 ) [ 8 ].…”