Engineering Biphenyl-Group Capping of Graphdiyne: Developing a Strategy for Assessing Polymerization Degree and Enhancing Photocatalytic Performance

Abstract

As a rising member of carbon allotropes, graphdiyne holds significant research value in terms of both its properties and applications. For properties, there is currently a lack of methods to assess the polymerization degree of graphdiyne, which is crucial to establish a standardized evaluation system for graphdiyne products; for applications, the application potential of graphdiyne materials with a low polymerization degree has not been fully explored. Herein, a biphenyl-group capping method has been engineered through the introduction of 4-ethynyl-1,1′-biphenyl (4-Eb) during the synthesis of hydrogen-substituted graphdiyne (GDY). 4-Eb could operate as a “capping agent” in the cross-coupling reaction, which tuned the polymerization degree of GDY. Accordingly, a strategy for relatively quantitatively assessing the polymerization degree of GDY via the precise analysis of Fourier transform infrared spectra (FTIR) has been developed and verified by various characterization methods. Moreover, the biphenyl-group capping could improve the separation efficiency of photogenerated carriers and introduce an intermediate energy level, which was helpful to expand the practical applicability of low-polymerization-degree graphdiyne materials in photocatalysis. Specifically, the photocatalytic degradation rate of the optimal sample for rhodamine B (RhB) was enhanced by 13.0-fold relative to GDY, and that for tetracycline hydrochloride (TCH) was increased by 4.9-fold.