Assembly of Lanthanide-Containing 3D [MnMo₉O₃₂]^6–-Based Metal–Organic Frameworks and Oxidative Desulfurization Performance

Lanthanide-containing polyoxometalate-based metal–organic frameworks (POMOFs) not only enjoy intriguing architectures but also have good application prospects as catalysts. Herein, three novel three-dimensional (3D) POMOFs with the formulas of {H[Ln₃(2,6-pydc)₂(H₂O)₁₀(MnMo₉O₃₂)]·2H₂O}_n (Ln = La(1), Pr(2), Nd(3)) have been synthesized based on Waugh-type [MnMo₉O₃₂]^6– anions and pyridine-2,6-dicarboxylate (2,6-H₂pydc). Compounds 1–3 are isomorphic, and there are two kinds of one-dimensional (1D) helical chains with opposite handedness staggered into two-dimensional (2D) layers. Interestingly, the coordinated L- and R-[MnMo₉O₃₂]^6– anions are encapsulated in 1D chains with the same chirality and are further expanded into 3D structures. The catalytic tests indicate that compounds 1–3 exhibit high-efficiency heterogeneous catalytic activity in the oxidative desulfurization reaction for catalyzing the oxidation of sulfides to sulfoxides using tert-butyl hydrogen peroxide (TBHP) as the oxidant. Moreover, a series of control experiments have been conducted to investigate the influence of various parameters such as temperature, time, solvent, catalyst, and substrate on the reaction. Significantly, compound 2, as an example, exhibits good reusability and structural stability in the oxidative desulfurization reaction. It is worth noting that investigations on the oxidative desulfurization of [MnMo₉O₃₂]^6– anions are scarce. Moreover, their electrochemical properties are also explored.