Robust Spin Liquidity in 2D Metal-Organic Framework Cu3 (HHTP)2 with S=1/2 Kagome Lattice

Abstract

On one hand electron or hole doping of quantum spin liquid (QSL) may unlock high-temperature superconductivity and on the other hand it can disrupt the spin liquidity, giving rise to a magnetically ordered ground state. Recently, a 2D MOF, Cu3(HHTP)2 (HHTP - 2,3,6,7,10,11-hexahydroxytriphenylene), containing Cu(II) S=urn:x-wiley:09476539:media:chem202303718:chem202303718-math-0001 frustrated spins in the Kagome lattice is emerging as a promising QSL candidate. Herein, we present an elegant in situ redox-chemistry strategy of anchoring Cu3(HHTP)2 crystallites onto diamagnetic reduced graphene oxide (rGO) sheets, resulting in the formation of electron-doped Cu3(HHTP)2-rGO composite which exhibited a characteristic semiconducting behavior (5 K to 300 K) with high electrical conductivity of 70 S ⋅ m−1 and a carrier density of ~1.1×1018 cm−3 at 300 K. Remarkably, no magnetic transition in the Cu3(HHTP)2-rGO composite was observed down to 1.5 K endorsing the robust spin liquidity of the 2D MOF Cu3(HHTP)2. Specific heat capacity measurements led to the estimation of the residual entropy values of 28 % and 34 % of the theoretically expected value for the pristine Cu3(HHTP)2 and Cu3(HHTP)2-rGO composite, establishing the presence of strong quantum fluctuations down to 1.5 K (two times smaller than the value of the exchange interaction J).