Solid solution approach to the design of copper mixed-triazolate multivariate-MOFs for the efficient adsorption of triclosan

Abstract

Employing solid solution approach, copper mixed-triazolate multivariate metal-organic frameworks CuMtz-2 {[Cu 8 (3,5-Ph 2 -tz) 6-x (3,5-Hm 2 -tz) x ](BF 4 ) 2 (CH 3 OH) 3 ; x = 0.6 for CuMtz-2a and 1.3 for CuMtz-2b; 3,5-Ph 2 -tz = 3,5-diphenyl-1,2,4-triazolate; 3,5-Hm 2 -tz = 3,5-dihydroxymethyl-1 H -1,2,4-triazolate} were successfully synthesized via a simple procedure of mixing a certain molar ratio of 3,5-Hm 2 -tzH and 3,5-Ph 2 -tzH with copper(I) salts at 303 K. After incorporation of 3,5-Hm 2 -tzH into the parent MOF CuTz-1 {[Cu 8 (3,5-Ph 2 -tz) 6 ](BF 4 ) 2 (CH 3 OH) 3 }, a significant enhancement of removal efficiency towards the adsorption of triclosan (TCS) was obtained over CuMtz-2 in comparison with that achieved over CuTz-1. Moreover, the adsorption capacity of TCS over CuMtz-2b (743.2 mg g −1 ) at 303 K is 128% of that over the pristine CuTz-1 (578.5 mg g −1 ) and far beyond than other reported MOF adsorbents. It is deemed that the hydrogen bond between 3,5-Hm 2 -tz and TCS plays the most important role during the adsorption. In addition, anion exchange between TCS − and BF 4 − also contributes to the enhanced adsorption performance at pH 9. More importantly, the used CuMtz-2b can be regenerated and applied for another three cycles without any obvious decline of activity towards removal of TCS. • Copper mixed-triazolate frameworks were prepared employing solid solution approach. • 3,5-dihydroxymethyl-1,2,4-triazolate substituted part of the ligand in CuTz-1. • The adsorption efficiency of triclosan was greatly improved by modified CuTz-1. • H-bonding played a vital role during the adsorption.