Efficient MO Dye Degradation Catalyst of Cu(I)-Based Coordination Complex from Dissolution–Recrystallization Structural Transformation
Ziyou Zhang, Guandong Zhang, Xi-Xi Sheng, Qian-Wen Ding, Yu-Zhuo Bai, Yan Su, Hong‐Ke Liu, Zhi Su
Abstract
Methyl orange (MO) is a main organic water pollutants that has been attracted a lot of attention; it can be degraded under photoirradiation in the presence of H2O2. Herein, we developed two Cu(I)-based coordination complexes (named H2(Cu4Br6)[(Cu4Br3)(TTTMB)2(H2O)]2 (ZZY-2) and (Cu5Br6)(Cu6Br9)[Cu3Br(TTTMB)2] (ZZY-3)), which could degrade the MO dye in the presence of H2O2 with or without photoirradiation (TTTMB = 1,3,5-tris(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene). Three-dimensional (3D) frameworks ZZY-2 and ZZY-3 were based on the molecule cage [Cu3(TTTMB)2] with the homochiral (−Cu–Br–Cu−)n triple-stranded helical chain and multinuclear Cu5Br6 and Cu6Br9 units, respectively, which could be obtained via the dissolution–recrystallization structural transformation (DRST) from two-dimensional (2D) network ZZY-1 ([Cu3(TTTMB)2(H2O)6Cl6]·2H2O). The addition of CuBr2 and the amount of HCOOH were decisive for the DRST, where the formation of a Cu–N coordination bond between the free 2-positional nitrogen atom and Cu(II) was the initiator for DRST. ZZY-2 and ZZY-3 had superior chemical stability, which could maintain the structures after three cycles of degradation reactions. MO degradation catalyzed by ZZY-2 and ZZY-3 could undergo a Fenton-like reaction to produce the active species •OH in the presence of H2O2. No requirement of photoirradiation for ZZY-2 and ZZY-3 to degrade MO provided more practical meaning to sewage treatment. Cu(II)-based ZZY-4 was also obtained as ZZY-1 in the presence of HNO3, which demonstrated the influence of acid on the structure of nitrogen-based ligands. ZZY-4 has shown no capacity to degrade MO, which indicated that the oxidation of Cu(I) by H2O2 could be the key step to initiate the MO degradation.