Regulating symmetry of organic precursors for mechanochemical synthesizing rich pyridonic-/pyridinic-nitrogen doped graphyne

Graphyne, a promising carbon candidate for energy storage and conversion, has been prepared successfully via a mechanochemical route. However, inevitable graphitic carbon species generate concomitantly. In this work, we synthesize rich pyridonic-/pyridinic-nitrogen doped graphyne (NGY) employing calcium carbide and asymmetric pentachloropyridine (PCP) as precursors and find that introducing symmetric hexabromobenzene (HBB) can suppress the formation of graphitic carbon impurities. The symmetry of organic precursors is a key to the yield of NGY during the mechanochemical process, so a competitive formation mechanism between NGY and graphitic carbon species is proposed according to experimental results and theoretical calculation. Compared with the samples obtained from single asymmetric PCP or symmetric HBB, an optimized NGY (1:1 molar ratio of PCP/HBB) increases the Li-storage capacity by 11% and 52% respectively, owing to abundant Li+ adsorption and high structural stability. This work highlights organic precursor symmetry for undergoing mechanochemical cross-coupling and brings new insights to in-situ constructing heteroatom-doped alkynyl carbon frameworks. We have demonstrated mechanochemical synthesizing nitrogen-doped graphyne, affording competitive lithium storage performance, and found that the feeding ratio of symmetric organic precursors is a key for suppressing inevitable graphitic carbon species. [Display omitted]