A water-based and high space-time yield synthetic route to MOF Ni-2(dhtp) and its linker 2,5-dihydroxyterephthalic acid
Résumé
2,5- Dihydroxyterephthalic acid (H(4)dhtp) was synthesized on an 189 scale by carboxylation of hydroquinone in molten potassium formate. The hydrated form of the Ni-2(dhtp) MOF (also known as CPO-27-Ni and MOF-74(Ni)) was obtained in 92% yield by refluxing for 1 h a water suspension of the H(4)dhtp linker with an aqueous solution of nickel acetate. The ensuing characterization of the material (XRD, HRTEM, TGA, N-2 adsorption at 77 K - S-BET = 1233 m(2) g(-1)) confirmed the formation of a metal-organic framework of at least equal quality to the ones obtained from the previously reported routes (CPO-27-Ni and MOF-74(Ni)), with a different morphology (namely, well-separated 1 mu m platelets for the herein reported water-based route). The temperature dependence of the magnetic susceptibility was measured and satisfactorily simulated assuming a Heisenberg (H = -2J Sigma SiSi+1) ferromagnetic intrachain interaction (J = +8.1 cm(-1)) and an antiferromagnetic interchain interaction (J' = -1.15 cm(-1)). Overall, the reaction in water appears to follow easily distinguishable steps, the first being the deprotonation of H(4)dhtp by an acetate counterion, leading to a soluble nickel adduct of the linker, en route to the MOF self-assembly.