Three CuI-Terpyridyl Coordination Polymers Regulated by π-Conjugated Groups and SCN– Anions for Organic Dye Photodegradation

Developing novel materials for organic dye photodegradation is of great significance in wastewater treatment. Three Cu^I-terpyridyl coordination polymers (CPs) [Cu₂(L1)(SCN)₂]_n (1), [Cu₃(L2)(SCN)₃]_n (2), and [Cu₂(L3)(SCN)₂]_n (3) (L1 = 4-(naphthalen-1-yl)-2,6-di(pyridin-4-yl)pyridine, L2 = 4-(anthracen-1-yl)-2,6-di(pyridin-4-yl)pyridine, L3 = 4-(pyren-3-yl)-2,6-di(pyridin-4-yl)pyridine), have been solvothermally synthesized and exhibit two-dimensional structures extended by Cu^I centers, SCN^–, anions, and terpyridyl ligands with different π-conjugated groups. Complexes 1–3 can decompose methylene blue (MB), Rhodamine B (RhB), and methyl orange (MO) with photodegradation rates ranging from 44.4 to 96.8% in 120 min. Owing to the more positive valence band potential and lower band gap regulated by Cu(I) d-electrons and pi-electrons of terpyridyl ligands, complex 2 exhibits the highest photocatalytic activity with the order of 2 > 1 > 3 and displays varied photodegradation efficiency for other dyes (Janus green B (JGB) and crystal violet (CV) with rates of 70.4 and 65.7% in 120 min, respectively). The degradation products and mechanism of MB by 2 have been proposed by liquid chromatography–mass spectrometry (LC-MS) and radical quenching experiments. These findings present an effective strategy for designing and synthesizing CPs in photodegradation by increasing the aromatic rings of π-conjugated groups and Cu^I center numbers, which may exert important impacts in wastewater treatment.