Long-Lived Electronic Spin Qubits in Two-Dimensional Conjugated Metal-Organic Frameworks

Two-dimensional conjugated metal–organic frameworks (2D c-MOFs) have attracted increasing interest in electronics due to their (semi)conducting properties. Charge-neutral 2D c-MOFs also possess persistent organic radicals that can be viewed as spin-concentrated arrays, affording new opportunities for spintronics and quantum information science. However, the strong π-interaction between neighboring layers of layer-stacked 2D c-MOFs annihilates active spin centers and significantly accelerates spin relaxation, severely limiting their potential as spin qubits. Herein, we report a series of molecular design strategies to tune the spin dynamics in 2D c-MOFs. The introduction of bulky side groups on the conjugated ligands enables a significant dislocation of the 2D c-MOFs layers from serrated stacking to staggered stacking, thereby spatially weakening the interlayer interactions. As a consequence, the electrical conductivity of 2D c-MOFs decreases by 6 orders of magnitude, while the spin density achieves more than a 30-fold increase and the spin–lattice relaxation time (<i>T</i>₁) is increased up to ∼60 μs, hence being superior to the reference 2D c-MOFs with compact stackings whose spin relaxation is too fast to be detected. Spin dynamics results also reveal that spinless polaron pairs or bipolarons play critical roles in the charge transport of these 2D c-MOFs. Furthermore, microsecond-scale coherence times at room temperature in a 2D c-MOF were achieved via framework engineering. Our strategy provides a bottom-up approach for enlarging spin dynamics in 2D c-MOFs, opening up pathways for developing MOF-based spintronics and quantum information science.<br/><br/>References:<br/>1. <i>Nat. Commun. </i><b>2022,</b> <i>13</i> (1), 7240.；<br/>2. <i>J. Am. Chem. Soc. </i><b>2024,</b> <i>146</i> (4), 2574-2582..