Designing 2D Fullerene Networks from C₇₀: A Stable and Synthesizable Platform for Electronic Band Engineering

Two-dimensional (2D) fullerene networks, assembled through covalent bonding of molecular fullerene building blocks, represent a rapidly emerging class of carbon-based nanomaterials with highly tunable topological structures and electronic properties. Here, we report the theoretical prediction of three 2D C₇₀ crystalline phases, two quasi-tetragonal phases (qTP1 and qTP2) and a quasi-hexagonal phase (qHP), formed through distinct covalent connections along the minor or major axis of ellipsoidal C₇₀ molecules. Comprehensive stability assessments confirm their thermodynamic, dynamic, and mechanical robustness, supported by feasible synthesis pathways analogous to those employed for the experimentally realized 2D C₆₀ networks. The qTP2 phase is identified as a rare semimetallic carbon network with intrinsic magnetism arising from sp² carbon atoms, while qTP1 and qHP possess ultranarrow band gaps. Our findings establish 2D C₇₀ as a versatile platform for engineering low-dimensional carbon-based quantum materials.