Effective regulation of the electronic properties of a biphenylene network by hydrogenation and halogenation

A biphenylene network, the first synthesized non-graphene planar carbon allotrope composed entirely of sp(2)-hybridized carbon atoms, has attracted widespread interest due to its unique structure, and electronic and mechanical properties. A pristine biphenylene network is metallic, and the effective regulation of its electronic properties will greatly expand its application in the fields of optoelectronics, nanoelectronic devices and photocatalysis. In this paper, the hydrogenation and halogenation of biphenylene networks were investigated using density functional theory, and their electronic properties were tuned by varying the functionalization concentration. Calculation results show that the maximum functionalization degree is CH(1.00), CF(1.00), CCl(0.67) and CBr(0.33), respectively. The band gap could be modulated in the range of 0.00–4.86 eV by hydrogenation, 0.012–4.82 eV by fluorination, 0.090–3.44 eV by chlorination, and 0.017–1.73 eV by bromination. It is also found that CH(x) (x = 0.92, 1.00), CF(x) (x = 0.75, 1.00), and CCl(x) (x = 0.42–0.67) have the potential to photolyse water. Our research indicates that hydrogenation and halogenation can effectively regulate the electronic properties of the biphenylene network by controlling the concentration of functionalization, thus expanding its potential applications in the field of electronic devices and photocatalysis.