A μ₄‐Oxo Bridged Tetranuclear Zinc Complex as an Efficient Multitask Catalyst for CO₂ Conversion

Abstract

A tetranuclear zinc complex having formula [Zn4(L)4(μ2‐OH2)2(μ4‐O)]⋅2TEAH⋅DMF⋅4H2O (1) has been synthesized from a benzothiazole based schiff base ligand. The complex was characterized by various spectroscopic and analytical techniques along with single crystal X‐ray diffraction (SCXRD) study. The crystal structure of the complex reveals that, there is formation of a tetranuclear dianionic core having metal centers in distorted trigonal bipyramidal (TBP) geometry supported by a μ4‐oxo and two μ2‐aqua bridgings. The μ4‐oxo acquires a special position, connecting to the zinc centers in a distorted tetrahedral (Td) fashion is mainly responsible for the higher nuclearity of the complex. The complex 1 exhibited multitask catalytic ability for CO2 utilization. It acts as an efficient catalyst for the conversion of various epoxides to cyclic carbonates as well as mimics carbonic anhydrase (CA) metalloenzyme. Hydrolysis of para‐nitrophenyl acetate (p‐NPA) was used as a model reaction to evaluate the CA activity. The complex also catalyzes the formation of bicarbonate (HCO3−) from CO2 by converting CaCl2 to CaCO3.

Effect of the proximal secondary sphere on the self-assembly of tetrahedral zinc-oxo clusters

“…A tetrahedral oxo-centered zinc carboxylate Zn 4 O(CO 2 ) 6 unit, as a prototypical node, has been particularly reticulated with various organic linkers into extended metal-organic frameworks (MOFs), including the archetypical MOF-5 9 , 10 . This type of metal-oxo clusters not only serve as directional and rigid building units but also can act as effective precursors of zinc oxide nanostructures 11 , gas absorption sites 12 – 14 , and efficient catalyst in transesterification of esters 15 – 18 , esterification of secondary amides 19 , acetylation and de-acetylation of carbohydrates 20 , direct conversion of esters, lactones, and carboxylic acids to oxazolines 16 , 21 , and CO 2 fixation to cyclic carbonates 22 – 25 . Therefore, an in-depth understanding of the multifaceted chemistry of zinc-oxo clusters supported by various types of organic ligands is continually vital for the development of various Zn-based functional materials.…”

Bio-Inspired Iron-Based Carbonic Anhydrase Mimic for CO2 Hydration and Conversion

“…To settle these issues, CA mimics arisen from supramolecules, − nanomaterials, − MOFs, , and polymers have been explored extensively. Due to the inherent active sites of natural CA, most of CA mimics are prepared by the coordination of zinc ions with azole derivatives, such as histidyl bolaamphiphile molecules (His-C7), , aza-macrocycle ligands, benzothiazole-based Schiff base ligands, triazoles, partially hydrophilic and hydrophobic tripod ligands, and so on. − In addition, CA mimics with other metals as active sites have also been introduced. For example, Zhang et al achieved efficient CO 2 capture by using a mixed-matrix membrane derived from Co-based CA mimics .…”

Carbonic anhydrase-mimicking metal–organic frameworks built from amino acid and cadmium ions

“…Some discrete zinc complexes were also made recently and show similar functions to CA. [15][16][17][18] Recently, there are a few reports on the study of MOFs as catalysts to simulate the structures and functions of CA, because they are excellent platforms for the assembly of functionalized architectures simulating structural and functional properties of enzymes. 4,6,7 These catalysts are usually ZIFbased MOFs.…”