Cu(II) and Zn(II) frameworks constructed by directional tuning of diverse substituted groups on a triazine skeleton and supermassive adsorption behavior for iodine and dyes.

The controllable design, synthesis and functional properties of a series of triazine tetratopic carboxylic MOFs have always been hotspots and challenges for research. Based on the characterization of the C-Cl bond on the triazine skeleton being easily substituted by some functional groups, we designed and synthesized a series of triazine tetratopic carboxylic Cu(II) and Zn(II) MOFs via the reaction of Cu(NO 3 ) 2 ·2.5H 2 O and ZnSO 4 ·7H 2 O, as well as triazine tetratopic carboxylic H 4 TDBA-Cl (H 4 TBDA-Cl = 5,5'-((6-chloro-1,3,5-triazine-2,4-diyl)bis(azanediyl))diisophthalic acid) under hydrothermal conditions. During the process of synthesizing, the C-Cl bond on the triazine skeleton of the ligand was substituted with different groups, which formed the complexes ([Cu 2 (TBDA-Cl)(H 2 O)·10DMF·30H 2 O] n ) (DMF = N , N -dimethylformamide) (1), N(Me) 2 -[(CH 3 ) 2 NH 2 ] 4 ·[Zn 3 (HTBDA-N) 2 (SO 4 ) 2 ] n (2) and H ([Cu 2 (TBDA-H)(H 2 O)] n ) (3), respectively. It is worth noting that the in situ substitution reaction occurred for complexes 2 and 3 during the process of synthesis. Also, the structural analysis showed that the molecules in complexes 1-3 were connected with different building blocks to form different three-dimensional structures. We performed iodine adsorption experiments on the three complexes and found that there was a significant relationship between the structural configuration and adsorption behaviour. The results showed that the complex 1 with the Cl atom on the triazine skeleton could have a boosting effect on adsorption with iodine. It displayed a remarkable adsorption effect for iodine (in the solution of water: 7.6 g g -1 and in the solution of cyclohexane: 548.2 mg g -1 ). In addition, it also displayed the adsorption effect for JGB dye (204.9 mg g -1 ). For complex 2, it displayed an uptake effect for iodine in the solution of cyclohexane (529 mg g -1 ). The possible adsorption mechanism was also investigated. By comparison, we found that chlorine atoms could play an important role in the adsorption processes. The adsorption capacity of complex 1 (containing the chlorine atom in the structure) was much higher than that for complex 3.