O-arylation reaction over lanthanide metal–organic framework: Synthesis, structure and catalytic reaction

Two novel lanthanide based two-dimensional metal-organic framework (MOF) compounds [Tb(NDC)(NO₃)(DMA)₂]_n (MOF-1) and [Ho(NDC)(NO₃)(DMA)₂]_n (MOF-2) [H₂NDC=2,6-naphthalenedicarboxylic acid and DMA=N,N-dimethylacetamide] have been synthesized following solvothermal route and structurally characterized. Structural analysis reveals that both the compounds are crystallized in the orthorhombic crystal system with space group Pbca. MOFs feature a “paddle-wheel” (PW) type core building units which are constructed via carboxylato oxygen coordination with lanthanide atoms. 2D lanthanide based MOFs consist of paddle-wheel building block are rare in the literature. MOF-1 and MOF-2 possess an octa-coordinated metal center. Apart from carboxylato groups, oxygen atoms of DMA and NO₃⁻ ions are also coordinated to metal centers. Paddle-wheel cores are interconnected to each other to give rise to layered network structure in both the cases. 2D layers are propagated parallel to bc plane and layers are stacked one upon another along the crystallographic a axis. Notably, both MOF-1 and MOF-2 are capable to catalyze O-arylation reaction efficiently under heterogeneous medium. However, amongst them, catalytic efficacy of MOF-1 towards O-arylation reaction is found to be better than that of MOF-2.