Open CdI2 sites in coordination polymers for HCl gas sensing

Abstract

The self-assembly of a tripod organic ligand L1 (1,3,5-tris(4′-pyridyloxadiazole)-2,4,6-triethylbenzene) with CdI2 gave rise to two one-dimensional wing like chain compounds depending on the ratio of CdI2 to L1. The produced 1 ([CdI2L1·EtOH], C35H33CdI2N9O4) obtained under low salt usage, was a zigzag chain with free pyridyloxadiazole flanking along the chain backbone. Increasing CdI2 content gave a helical chain 2, ([Cd4I8(L1)2(EtOH)2·(EtOH)3], C76H84Cd4I8N18O11) with wings capped with terminal CdI2 sites. Further tests revealed that the terminal CdI2 were more open and sensitive to HCl gas, which can be transformed to iodine species with naked-eye color change. This work clearly demonstrated one-dimensional coordination polymers as active site support for potential toxic gas sensing applications.