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As a new member of the carbon family,graphdiyne is an intrinsic semiconductor featuring a natural bandgap,which endues it potential for direct application in photoelectric devices.However,without cooperating with other active materials,conventional hexacetylene-benzene graphdiyne (HEB-GDY) shows poor performances in photocatalysis and photoelectric devices due to its non-ideal visible light absorption,low separation efficiency of the photogenerated carriers and insufficient sites for hydrogen production.Herein,we report a molecular engineering strategy for the regulation of GDY-based carbon materials,by incorporating a strong pyrene absorption group into the matrix of graphdiyne,to obtain pyrenyl graphdiyne (Pyr-GDY) nanofibers through a modified Glaser-Hay coupling reaction of 1,3,6,8-tetraethynylpyrene (TEP) monomers.For comparison,phenyl graphdiyne (Phe-GDY) nanosheets were also constructed using 1,3,4,6-tetraethynylbenzene (TEB) as a monomer.Compared with Phe-GDY,Pyr-GDY exhibits a wider visible light absorption band,promoted efficiency of the charge separation/transport and more sufficient active sites for water reduction.As a result,Pyr-GDY alone displays superior photoelectrocatalytic performance for water splitting,giving a cathode photocurrent density of ～138 μA cm-2 at a potential of-0.1 Vversus normal hydrogen electrode (NHE) in neutral aqueous solution,which is almost ten and twelve times as high as those of Phe-GDY (14 μA cm-2) and HEB-GDY (12 μA cm-2),respectively.Such a performance is also superior to those of most reported carbonbased metal-free photocathode.The results of theoretical calculations reveal that the carbon atoms in the acetylene bonds are the active sites for proton reduction.This work offers a new strategy for the construction of graphdiyne-based metal-free photoelectrocatalysts with enhanced photoelectrocatalytic performance.