Orbital Selective Large Magnetic Anisotropy, Valley Polarization, and Antiferromagnetic Dirac‐Mott Insulators in 2D Metal–Organic Frameworks with a Ruby Lattice

Abstract 2D lattice structures, such as honeycomb, kagome, and Lieb lattices, as well as their notable band structures, have attracted considerable attention due to their potential for investigating multifunctional quantum states. The high tunability of 2D metal–organic frameworks (MOFs) provides ideal platforms for the experimental realization of these lattice structures and their novel quantum properties. Based on first‐principles calculations, a series of stable 2D TM‐HOB MOFs is constructed, featuring a unique ruby lattice that can spontaneously assemble using H 6 HOB (hexahydroxybenzene) species and three‐fold coordinated transition metal atoms (TM = Ti, V, Cr, Mn, Fe, Ni, Zr, Nb, and Hf) through a deprotonation process. In these 2D TM‐HOB MOFs, the transition metal ions reside within a planar triangular crystal field, which results in d orbital splitting into three groups: e′( d xy/x2‐y2 ), a′( d z2 ), and e′″( d xz/yz ). By modulating the relative positions of the Fermi level and the three groups of d orbitals, a range of emergent phenomena arises, including an orbital‐selective huge magnetic anisotropy energy in Ni‐HOB (163.54 meV Ni −1 ), remarkable valley splitting in Fe‐HOB (388 meV), and antiferromagnetic Dirac‐Mott insulators in Zr‐HOB and Hf‐HOB. This study provides promising material candidates for the development of spintronics, valleytronics, and quantum computing.