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 (NO3)(2)center dot 2.5H(2)O and ZnSO4 center dot 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)(H2O)center dot 10DMF center dot 30H(2)O](n)) (DMF = N,N-di-methylformamide) (1), N(Me)(2) -[(CH3)(2)NH2](4)center dot[Zn-3(HTBDA-N)(2)(SO4)(2)](n) (2) and H ([Cu-2(TBDA-H)(H2O)](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.