Secondary Building Unit (SBU) Controlled Formation of a Catalytically Active Metal–Organic Polyhedron (MOP) Derived from a Flexible Tripodal Ligand

A nanosized truncated octahedron-shaped metal–organic-polyhedron (MOP) namely [{Cu12(TMBTA)8(DMA)4(H2O)8}·8H2O·X] MOP-TO (X = 48 H2O molecules as per SQUEEZE calculation and TGA data) was successfully derived from a flexible C3-symmetric ligand (2,4,6-trimethylbenzene)-1,3,5-triacetic acid (TMBTA) and Cu­(NO3)2 in dimethyl acetamide (DMA) and EtOH under solvothermal conditions. The nanocage was well-characterized by single crystal X-ray diffraction (SXRD) and electron spray ionization mass spectrometry (ESI-MS). Remarkably, the nanocage molecules could be seen under high-resolution transmission electron microscope (HR-TEM). It was evident that the Cu­(II) paddle wheel secondary building unit (CPWSBU) was responsible for the formation of the nanocage, as the corresponding reactions of TMBTA with other metal ions (e.g., Co­(II) and Zn­(II) resulted in the formation of two coordination polymers, namely [{Co­(μ-TMBTA)­(H2O)4}]∝ TMBTA-Co­(II) and [{(H2O)2Zn­(μ-TMBTA)­Zn·K}·2H2O]∝ TMBTA-Zn­(II). Interestingly, the nanocage MOP-TO was exploited in catalyzing (2,2,6,6-tetramethylpiperidin-1-yl)­oxy (TEMPO)-assisted aerobic oxidation of benzyl alcohol to benzaldehyde.