Atomistic Approach towards Selective Photocatalytic Oxidation of a Mustard-Gas Simulant: A Case Study with Heavy-Chalcogen-Containing PCN-57 Analogues

Goswami, S.; Miller, C. E.; Logsdon, J. L.; Buru, C. T.; Wu, Y.-L.; Bowman, D. N.; Islamoglu, T.; Asiri, A.; Cramer, C. J.; Wasielewski, M. R.; Hupp, J. T.; Farha, O. K.
ACS Appl. Mater. Interfaces 2017, 9, 19535 (doi:10.1021/acsami.7b07055).

Here we describe the synthesis of two Zr-based benzothiadiazole- and benzoselenadiazole-containing metal-organic frameworks (MOFs) for the selective photocatalytic oxidation of the mustard gas simulant, 2-chloroethyl ethyl sulfide (CEES). The photophysical properties of the linkers and MOFs are characterized by steady-state absorption and emission, time-resolved emission, and ultrafast transient absorption spectroscopy. The benzoselenadiazole-containing MOF shows superior catalytic activity compared to that containing benzothiadiazole with a half-life of 3.5 min for CEES oxidation to nontoxic 2-chloroethyl ethyl sulfoxide (CEESO). Transient absorption spectroscopy performed on the benzoselenadiazole linker reveals the presence of a triplet excited state, which decays with a lifetime of 9.4 μs, resulting in the generation of singlet oxygen for photocatalysis. This study demonstrates the effect of heavy chalcogen substitution within a 27 porous framework for the modulation of photocatalytic activity.