Internally extended growth of core-shell NH2-MIL-101(Al)@ZIF-8 nanoflowers for the simultaneous detection and removal of Cu(II)

The excessive accumulation of toxic copper species makes it imperative to develop smart dual-functional materials for the simultaneous removal and detection of Cu(II) in drinking water. In this work, novel core-shell NH2-MIL-101(Al)@ZIF-8 nanoflowers were successfully fabricated via an internal extended growth mode under the regulation of polyvinylpyrrolidone (PVP) to achieve this goal. Benefiting from the specific affinity of imidazole nitrogen in ZIF-8 toward Cu(II), the resultant NH2-MIL-101(Al)@ZIF-8 shows high adsorption capacity (526.74 mg g(-1)). Moreover, the fluorescence of NH2-MIL-101(Al) shows a Cu(II)-dependent change, causing this composite to possess superior selective/sensitive detection with a broad linear range (1.5-625 mM) and a low detection limit (0.17 mM) for Cu(II). Specifically, the hybrid MOF@MOF structure provides greater sensitivity as compared to the individual constituent (pristine NH2-MIL-101(Al)) and the mixed state, which is ascribed to the rational optimization of the smart adsorbent based on the following two aspects. (i) The synergistic effect of the core-shell nanostructure improves the preconcentration ability at the interface between single MOFs. (ii) The existence of the three-dimensional hierarchical nanoflower architecture (structure optimization) accelerates the mass transport and sculpts the final composite with enhanced adsorption and detection ability. These indicate that the smart NH2-MIL-101(Al)@ZIF-8 nanoflower could be an excellent candidate for the synchronous remediation and selective detection of Cu(II) in aqueous systems, which could be potentially useful in wastewater treatment and water quality monitoring.