Biphenylene-Based Crystalline Foam Carbon Allotropes

Developing new allotropes with excellent
properties and
high synthesizability
is an intriguing and challenging topic for carbon materials. Based
on the experimental biphenylene monolayers, varied three-dimensional
crystalline foam carbon allotropes with parallel channels in the structure
are theoretically designed. These calculated foam carbon structures
are mostly semimetals or semiconductors. The selected representatives
possess lattice dynamic stability, high thermal stability, great mechanical
performance stability, and feasible synthesizability. Moreover, the
selected foam carbon structures exhibit high feasibility in ion filtration,
transport, or storage for different ion species. The representative
structure (3D-C48-Z2-R4R4-R6-trans) exhibits a high theoretical lithium storage
capacity of 930.6 mAh·g–1, low diffusion barriers
of only 0.079 eV, suitable open-circuit voltage of 0.905–0.071
V, and relatively small volume change (8.5%). Besides, a nonfoam-limit
structure (BPN-diamond) is found to be a direct bandgap semiconductor
with a bandgap of 4.073 eV (HSE06), exhibiting ultrahigh hardness
(HV ∼ 76.4 GPa), high carrier mobility
(up to 5.97 × 103 cm2 V–1 s–1), good optical absorption ability in the UV
region, and high synthesizability. These findings suggest that the
biphenylene-based foam carbon allotropes are potentially excellent
multifunctional materials with applications in flexible and ductile
materials, ion electron mixed conductors, ion filtration, and anode
materials for Li ion batteries.