Transient absorption spectroscopy and photochemical reactivity of CAU-8

Abstract

CAU-8 is a metal organic framework with the composition [Al(OH)(BPDC)] (BPDC: 4,4′-benzophenone dicarboxylate) whose structure is constituted by chains of corner-sharing AlO₆ octahedra connected by BPDC linkers, giving rise to an array of non-intersecting channels. According to the well known photochemical behavior of benzophenone, in the present study we have been able to obtain spectroscopic evidence of the photochemical reactivity of CAU-8, including the generation of short-lived triplet excited states that react with either electron donors (triethylamine) or hydrogen donors (isopropanol) and lead to the corresponding radical anions or ketyl radicals, respectively. These two species have long half live times in CAU-8 and their decay is not complete hundreds of microseconds after the laser pulse. The photochemical activity of the BPDC linker in CAU-8 has been used to promote the radical-induced (co)polymerization of styrene and the coupling of BPDC and ethanol has been followed with IR spectroscopy.