The thriving area of synthetic carbon allotropes witnesses theoretic proposals and experimental syntheses of many new two-dimensional monolayer structures, which are often achieved by careful arrangement of non-hexagon sp² defects in graphene. Here, we introduce pyramid sp³ hybridization into sp² network and propose a new carbon polymorph with clathrate pattern and minimum egg-tray shape (termed as clathrate graphene). Eight symmetrically equivalent sp² carbon atoms and two symmetrically equivalent sp² carbon atoms in its tetragonal primitive unit cell form two perpendicularly oriented rectangles and four bridging hexagons. Though deformed bond lengths and bond angles, the planar geometry of all tetrarings and hexagons are retained. High percentage and small deformation of hexagons make this metastable sp²-sp³ allotrope comparable with sp² T-graphene and penta-graphene in energetics. Exhaustive ab initio calculations confirm its dynamical and elastic stabilities, reveal its semiconducting nature with an indirect band gap of 0.90 eV in PBE level (1.90 eV in HSE06 level) for unstressed sample. Strain effects on the elastic and electronic properties of this allotrope are also studied, an ultrahigh ideal strength that outmatches graphene and a giant strain tuning effect on its bandgap are observed. These salient properties may imply potential nanoelectronic applications. Our findings help understand structure-property relationship for two-dimensional carbon allotropes, and help search new carbon polymorphs.

合成碳同素异形体的蓬勃发展见证了许多新的二维单层结构的理论建议和实验合成，这通常是通过精心安排石墨烯中非六方sp ²缺陷来实现的。在这里，我们将金字塔sp ³杂交引入sp ²网络，并提出了一种具有笼形图案和最小蛋盘形状的新型碳多晶型物（称为笼形石墨烯）。八个对称等效的sp ²碳原子和两个对称等效的sp ²在其四边形原始晶胞中的碳原子形成两个垂直定向的矩形和四个桥接六边形。尽管键长和键角变形，但所有四环和六边形的平面几何形状均得以保留。六边形的百分比高且变形小，使该亚稳态sp ² -sp ³同素异形体在能量学上可与sp ² T-石墨烯和五石墨烯相媲美。详尽的从头算计算证实了它的动力学和弹性稳定性，揭示了其半导体性质，在无应力样品中，PBE水平的间接带隙为0.90 eV（HSE06水平的为1.90 eV）。还研究了应变对这种同素异形体的弹性和电子性能的影响，观察到了超高的理想强度，该强度超过了石墨烯，并且观察到了对其带隙的巨大应变调节作用。这些显着特性可能意味着潜在的纳米电子应用。我们的发现有助于理解二维碳同素异形体的结构-性质关系，并有助于寻找新的碳多晶型物。