Constructing of fragmentary g-C3N4 framework with rich nitrogen defects as highly efficient metal-free catalyst for acetylene hydrochlorination

Graphitic carbon nitride (described as “g-C3N4”) as a graphite-like CN material, is widely used in catalysis. In this paper, a fragmentary g-C3N4 framework with porous structure and rich nitrogen defects was synthesized for acetylene hydrochlorination, using melamine-formaldehyde (MF) resin as oxygen-containing precursor. The fragmentary g-C3N4 shows highly efficient activity with acetylene conversion reaching 94.5%, which is 30 times higher than pure g-C3N4 prepared by direct pyrolysis of melamine. Both experimental and characterization studies of XRD, XPS and TG-MS reveal that the high activity of catalyst is mainly derived from the porous structure and rich nitrogen defects, which were attributed to the etching of g-C3N4 framework by oxygen species in MF resin. Moreover, density functional theory (DFT) calculations demonstrated that the nitrogen defects in g-C3N4 framework greatly improved the adsorption of HCl and acetylene, and at the same time significantly reduced the energy barrier from 62.0 to 38.1 kcal·mol–1 at rate-determining step.