Pillar-Layered Metal–Organic Frameworks Based on a Hexaprismane [Co6(μ3-OH)6] Cluster: Structural Modulation and Catalytic Performance in Aerobic Oxidation Reaction

Abstract

Embedding a functional metal-oxo cluster within the matrix of metal–organic frameworks (MOFs) is a feasible approach for the development of advanced porous materials. Herein, three isoreticular pillar-layered MOFs (Co6-MOF-1–3) based on a unique [Co6(μ3–OH)6] cluster were designed, synthesized, and structurally characterized. For these Co6-MOFs, tuning of the framework backbone was facilitated due to the existence of second ligands, which results in adjustable apertures (8.8 to 13.4 Å) and high Brunauer–Emmett–Teller surfaces (1896–2401 m2 g–1). As the [Co6(μ3–OH)6] cluster has variable valences, these MOFs were then utilized as heterogeneous catalysts for the selective oxidation of styrene and benzyl alcohol, showing high conversion (>90%) and good selectivity. The selectivity of styrene to styrene oxide surpassed 80% and that of benzyl alcohol to benzaldehyde was up to 98%. The calculated TOF values show that the increase of reaction rate is positively correlated with the enlargement of pore sizes in these MOFs. Further, a stability test and cycling experiment proved that these Co6-MOFs have well-observed stability and recyclability.

A theorized new class of polyhedral hydrocarbons of molecular formula CnHn and their bottom-up scaffold expansions into hyperstructures

“…So, for all practical purposes, it is very unlikely that the hexaprismane hydrocarbon nugget 12 could ever be of practical use as a chemical voxel. Nevertheless, the geometric concept of an hexaprismane polyhedron as a chemical voxel has recently been realized by the synthesis of isoreticular pillar layered metal organic frameworks exhibiting properties such as catalytic activity 37 . Two other self-dissociation reactions that could be thought of for the hexaprismane nugget 12 would be: (i) self-dissociation Fig.…”

Customized Synthesis of MOF Nanoplates via Molecular Scalpel Strategy for Efficient Oxygen Reduction in Zn−Air Batteries

“…As the Lewis basicity of the nitrogen atom in pyridine (pK a = 5. 19) is stronger than that in bpy (pK a1 = 3.17; pK a2 = 4.82), the bpy in 1 could be displaced with pyridine. As expected, capping pyridine ligand was seen to efficiently replace the bpy and chemically split the layers of 1 to usefully produce 2D MOF nanoplates with uniform thickness.…”

“…With this hypothesis in mind, we prepared a 3D MOF of {[Co 6 (OH) 6 (TCA) 2 (bpy) 3 ]} n (1) (bpy = 4,4'bipyridine, H 3 TCA = 4,4',4''-tricarboxyltriphenylamine). [19] In 1, six cobalt (II) ions are coordinated with six μ 3 -OH to form Co 6 (μ 3 -OH) 6 (Figure S1) acting as secondary building units (SBUs). The TCA ligand serves as a 3-connecting node connected with three Co 6 (μ 3 -OH) 6 SBUs comprising 2D layers (Figure S2), which is further connected with the adjacent 2D layers by bpy pillars to generate a 3D MOF.…”

Metal Organic Frameworks as Heterogeneous Catalysts in Olefin Epoxidation and Carbon Dioxide Cycloaddition

“…The hexaprismatic [Co 6 (µ 3 −OH) 6 ] cluster with different variable valences activate the oxygen molecule for aerobic epoxidation of alkenes [28]. In Co6-MOF-3, large pores facilitated the mass transfer giving the fastest reaction rate with high conversion and good selectivity for oxidation of both styrene and benzyl alcohol [29].…”