Metal-free carbon nitride(CN) polymers have gained considerable attention recently due to their low prize and potential energy-related applications, including water splitting, batteries, fuel cells, sensors, photo and electrocatalysis, CO₂ reduction, and more^[1]. One classic route to synthesize these materials is via solid-state approach (pyrolysis of pristine solid monomers at high temperatures). Despite the impressive wide range of materials synthesized by this method there are still some drawbacks that limit the progress in this field. The solid-state approach often results in low porosity, unordered materials with grain boundaries and arbitrary morphology.

During the past few years, great achievements in the controlled CN design have been obtained through hard and soft templating and by using supramolecular complexes as CN precursors. Recently our group and others showed the use of crystalline precursors to control the CN synthesis toward an efficient photocatalyst for water splitting application.^[2] This synthetic approach allows to tailor CN morphology, electrical, chemical as well as photophysical properties and open a window to create crystalline CN materials with reduced number of grain boundaries, defects and trapping sites on the materials surface. The later leads to better charge separation and improved photo-activity performances.

Moreover, the introduction of different heteroatoms into CN matrices is a versatile tool for tuning its chemical and physical properties toward the formation of a large array of materials.^[3] For example, inserting phosphorous atoms into CN materials enables the modification of various properties such as: electrical conductivity, oxidation stability and photocatalytic performance, due to the insertion of atoms with different electronegativity and radius size, into the CN network. The synthesis of these phosphorous nitrogen carbon (PNC) materials is complicated as phosphorus large covalent radius hampers its incorporation into the CN network and achieving its successful inclusion beyond the trace level stands as a current challenge.^[4] Here we show a simple and large scale synthesis to develop phosphorus-rich PNC materials with tunable properties as well as elemental composition by using organic phosphoric acid-melamine crystals as PNC precursors. The new synthetic tool allows the fine-tuning of the morphology, chemical, thermal stability, electronic properties, and (photo)electrocatalytic activity toward the development of wide variety of materials ranging from polyphosphazenes to phosphorous and nitrogen doped carbon. The resulted PNC materials demonstrate remarkable thermal stability and their potential photocatalytic activity will be tested.