Adsorption behavior and mechanism of Hg (II) on a porous core-shell copper hydroxy sulfate@MOF composite

Herein, a porous core-shell copper hydroxy sulfate@metal-organic framework decorated by 2,5-dimercapto1,3,4-thiadiazol (DMTZ) was synthesized via a facile self-template strategy for the capture of Hg2+. The strategy of assembling MOF shell on copper hydroxy sulfate (CHS) core avoided the self-nucleation of MOF(Cu-3(BTC)(2)) in the solution and complex multistep procedures by means of in situ transformation the metal source CHS into well-defined Cu-3(BTC)(2) crystal. The structure and properties of the DMTZ modified CHS@Cu-3(BTC)(2) (CHS@Cu-3(BTC)(2)-DMTZ) was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA) and N-2 sorption-desorption isotherms (BET). The adsorption behavior followed Langmuir adsorption model and the maximum adsorption capacities for the removal of Hg2+ was up to 627.6 mg g(-1). 99.96% Hg2+ was rapidly captured by CHS@Cu-3(BTC)2-DMTZ within 10 min from 40 mg L-1 to 0.014 mg L-1. Meanwhile, not only X-ray photoelectron spectroscopy (XPS) but also Raman spectra verified the selective and strong interaction between Hg2+ and thiol/nitrogen-containing functional groups of DMTZ on CHS@Cu-3(BTC)(2)-DMTZ. These results manifested that this novel thiol-functionalized MOF adsorbent had superior adsorption capacity and selective for Hg2+.

Automated summary

A porous core-shell copper hydroxy sulfate@metal-organic framework with surface decoration of 2,5-dimercapto1,3,4-thiadiazol was synthesized for the capture of Hg2+ using a self-template strategy, exhibiting superior adsorption capacity and selectivity. The adsorption behavior followed the Langmuir adsorption model, with a maximum adsorption capacity of 627.6 mg g(-1) for Hg2+ removal, and rapid capture of 99.96% Hg2+ within 10 minutes. XPS and Raman spectra confirmed the selective and strong interaction between Hg2+ and the functional groups on the modified MOF adsorbent.