Copper(II) pseudoatrane appended heterobimetallic 2D‐MOF: A multi‐functional material with catalytic and sensing properties

Abstract

A maiden two‐dimensional atrane‐based heterobimetallic MOF (2) was constructed employing a novel tripodal ligand N{CH2COOH}2{CH2(2‐t‐Bu‐4‐CH3‐C6H2‐OH)} (1). Single‐crystal X‐ray diffraction depicted the formation of [4.3.3.01,5] pseudoatrane cage in which copper(II) ions attained trigonal bipyramidal geometry. Besides, the co‐existing sodium(I) ions acquired a pentagonal bipyramidal geometry produced by methanol molecules and free carboxylate sites of the ligand. This compound is the first of its kind where the sequential binding of copper(II) pseudoatrane cage and hepta‐coordinated sodium ion generated a heterobimetallic metal–organic framework with a sheet‐like structure. The TEM and SEM images of the MOF having stability up to 250°C revealed the formation of spherical structures (~78 nm) with flower‐like morphology. The heterobimetallic 2D‐MOF was proved to be a multifunctional material as it successfully catalysed Friedel–Craft's alkylation of Indole with beta‐nitrostyrene as well as utilised for the efficient detection of toxic brominated flame retardants through spectrophotometric and colorimetric studies. Remarkably, the best catalysis results were seen using DCM as a solvent, and the alkylation product obtained from the reaction of 2‐methylindole with 2‐Br‐β‐nitrostyrene showed an extraordinary yield of 98%. Besides, the 2D‐MOF showed a selective response with pentabromophenol, and tetrabromophthalic anhydride with quenching in peak on the addition of TBPA while shifting of the peak was observed from 457 to 402 nm with PBP. The practical application of the MOF was explored by its successful incorporation into portable silica strips for on‐the‐spot detection of BFRs.