Anion-Directed Self-Assembly of Calix[4]arene-Based Silver(I) Coordination Polymers and Photocatalytic Degradation of Organic Pollutants

Coordination polymers (CPs) have recently emerged as promising candidates for heterogeneous photocatalysis due to their structural designability and tunable properties. Herein, we developed two novel Ag(I)-calix[4]arene coordination polymers with the formula {[Ag2(mu-NO3)L1]}n (CP 1) and {[AgL1]center dot PF6}n (CP 2) (L1 = 2-mercapto-5-methyl-1,3,4-thiadiazole resorcinol calix[4]arene). Crystallography revealed that anion coordination and self-inclusion behavior induced the cavitand and silver ions to self-assemble into well-defined CPs 1 and 2 with different topological coordination frameworks, respectively. Furthermore, CPs 1 and 2 display high photocatalytic activity for the photodegradation of rhodamine B (RhB) and methyl orange (MO) in an aqueous solution under mild conditions (WLED and UV irradiation). The comparison results demonstrate that CP 1 exhibited better photocatalytic performance than CP 2, which correlated well with the differences in their molecular structure and HOMO-LUMO energy gaps. The photocatalysis products and possible intermediates were successfully monitored and determined using mass spectrum, gas chromatography, and electron paramagnetic resonance measurements. The rational photocatalysis mechanism was further investigated and proposed.

Automated summary

Two novel Ag(I)-calix[4]arene coordination polymers were developed and exhibited well-defined coordination frameworks due to the anion coordination and self-inclusion behavior. CPs 1 and 2 showed high photocatalytic activity for the degradation of RhB and MO under mild conditions (WLED and UV irradiation). CP 1 outperformed CP 2 in photocatalytic performance, which correlated with their molecular structure and HOMO-LUMO energy gaps. The photocatalysis mechanism was investigated and proposed, and the products and intermediates were successfully monitored and determined.