Spin-Gapless Semiconductors and Quantum Anomalous Hall Effects of Tetraazanaphthotetraphene-Based Two-Dimensional Transition-Metal Organic Frameworks on Spintronics and Electrocatalysts for CO2 Reduction

Abstract

The two-dimensional metal–organic framework (2D MOF) has potential applications in spintronics and catalytics due to the tunable structure, high crystallinity, and porosity. However, the study of the physical properties of a precise single-crystal 2D MOF is rare because of the small crystals or poor quality, which hinders the practical application. In this work, based on the successful fabrication of 200 μm single-crystal 2D Cu3(HHTT)2 and Ni3(HHTT)2 (HHTT = 2,3,7,8,12,13-hexahydroxy tetraazanaphthotetraphene), the electronic, magnetic, and catalytic properties of 2D M3(HHTT)2 (M = 3d transition metals) were studied by first-principles calculations. Cr3(HHTT)2 and Cu3(HHTT)2 exhibit out-of-plane ferromagnetic spin-gapless semiconductor properties with opposite spin polarization. When the spin-orbit coupling is considered, Cr3(HHTT)2 opens a gap of 3.37 meV around the Fermi level and shows a quantum anomalous Hall effect with the Chern number C = 1. Cr3(HHTT)2 shows a lower overpotential (0.66 eV) than that of Cu3(HHTT)2 (1.94 eV) for electrocatalytic CO2 reduction reactions. Additionally, Mn3(HHTT)2 exhibits robust out-of-plane ferrimagnetic semiconducting properties. M3(HHTT)2 (M = Ti, Fe, and Co) and V3(HHTT)2 exhibit in-plane spin-gapless semiconductor properties with an opposite spin polarization. These results provide candidates for the study of spintronics and electrocatalysts.