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 {[Cu8(3,5-Ph2-tz)6-x(3,5-Hm2-tz)x](BF4)2(CH3OH)3; x = 0.6 for CuMtz-2a and 1.3 for CuMtz-2b; 3,5-Ph2-tz = 3,5-diphenyl-1,2,4-triazolate; 3,5-Hm2-tz = 3,5-dihydroxymethyl-1H-1,2,4-triazolate} were successfully synthesized via a simple procedure of mixing a certain molar ratio of 3,5-Hm2-tzH and 3,5-Ph2-tzH with copper(I) salts at 303 K. After incorporation of 3,5-Hm2-tzH into the parent MOF CuTz-1 {[Cu8(3,5-Ph2-tz)6](BF4)2(CH3OH)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-Hm2-tz and TCS plays the most important role during the adsorption. In addition, anion exchange between TCS− and BF4− 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.