Ligand-engineered copper-based triazolate MOFs: enhanced adsorption performance for methyl blue removal

A series of copper triazolate metal-organic frameworks (MOFs), denoted as CuTz-1_X (X = CH 2 OH, Py, and FPh), were synthesized via doping functionalized triazole ligands (3,5-R 2 -tzH where R = CH 2 OH, Py, or FPh) into the reactant of parent CuTz-1 ([Cu 8 (3,5-Ph 2 -tz) 6 ](BF 4 ) 2 (CH 3 OH), where 3,5-Ph 2 -tz = 3,5-diphenyl-1,2,4-trizolate). The synthesized MOFs were thoroughly characterized via PXRD, 1 H NMR, SEM-EDS, EA, TG, etc. It was observed that doping ligands featuring similar size and structure with 3,5-diphenyl-1,2,4-triazole in the parent MOF CuTz-1 resulted in a higher incorporation quantity. Furthermore, the introduction of functional ligands into the modified MOFs, CuTz-1_X, led to enhanced adsorption performance for the removal of methyl blue (MeB) in comparison with that observed over the parent MOF. Especially, CuTz-1_Py, in which 3,5-bis(4-pyridinyl)-1,2,4-triazole was doped, exhibited the highest MeB adsorption capacity of 352.3 mg·g − 1 at 293 K. Besides, the adsorption capacity of MeB over CuTz-1_X MOFs materials maintained stable even in the simulated real water systems. More importantly, the adsorption efficiency of MeB over CuTz-1_Py was still 87 % after four cycles of adsorption experiments while preserving the crystallinity and morphology of the adsorbent, indicating that the modified MOFs materials (i.e. CuTz-1_X) could be promising candidates for wastewater treatment.