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EBT anchored SiO2 3-D microarray: a simultaneous entrapper of two different metal centers at high and low oxidation states using its highest occupied and lowest unoccupied molecular orbital, respectively†
Bhavya Srivastava,Milan K. Barman,Mousumi Chatterjee,Bhabatosh Mandal
RSC Advances Pub Date : 06/05/2015 00:00:00 , DOI:10.1039/C5RA07103H
Abstract

A quick and facile synthesis of a mesoporous (pore diameter = 46.2–47.1 nm) material (FSG-EBT) through the immobilization of azo dye (EBT) on functionalized silica gel (FSG) has been achieved. FSG-EBT simultaneously binds two different metal centers, Zr(IV) and Tl(I) at their high and low oxidation states, respectively. Highest occupied molecular orbital (HOMO) of the extractor binds Zr(IV) with a breakthrough capacity (BTC) of 490 μmol g−1 and its lowest unoccupied molecular orbital (LUMO) extracts Tl(I) (BTC = 120 μmol g−1). The LUMO has thus enhances the BTC of the resin as a whole. This binding mode sequence differs from earlier existing mode of binding where extractors bind metals using HOMO and LUMO operative on the same metal centre only. HOMO/LUMO value (μmol g−1) reiterates itself as a definite quantum mechanical descriptor of BTC, and BTC is a definite descriptor of the state of metal (monomer/polymer) sorbed. The synthesis needs no stringent reaction condition such as refluxing. Its corresponding nanomaterial has been well assessed (composition: [Si(OSi[triple bond, length as m-dash])3(OH)·xH2O]n[–Si(CH3)2–NH–C6H4–N[double bond, length as m-dash]N–EBT]4; structure: tetrahedral) and is reiterated by density functional theory (DFT) calculation. Along with its good extractor qualities [high pore volume, PV = 0.3747 cm3 g−1; surface area, SA = 330.97 m2 g−1; BTC (Q0 = 476.7 μmol g−1); column efficiency, CE = 296 and preconcentration factor, PF = 120.20 ± 0.04; reusability > 1000 cycles; and faster rate of sorption–desorption], FSG-EBT possesses well demarcated spatial placement of HOMO–LUMO with a substantial band gap (η = 7.1471 eV). This makes charge recombination by mixing difficult and thus shows its potential applicability as a good donor–acceptor organic electronic device.

Graphical abstract: EBT anchored SiO2 3-D microarray: a simultaneous entrapper of two different metal centers at high and low oxidation states using its highest occupied and lowest unoccupied molecular orbital, respectively
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