Triplet Generation Through Singlet Fission in Metal‐Organic Framework: An Alternative Route to Inefficient Singlet‐Triplet Intersystem Crossing

Abstract High quantum yield triplets, populated by initially prepared excited singlets, are desired for various energy conversion schemes in solid working compositions like porous MOFs. However, a large disparity in the distribution of the excitonic center of mass, singlet‐triplet intersystem crossing (ISC) in such assemblies is inhibited, so much so that a carboxy‐coordinated zirconium heavy metal ion cannot effectively facilitate the ISC through spin‐orbit coupling. Circumventing this sluggish ISC, singlet fission (SF) is explored as a viable route to generating triplets in solution‐stable MOFs. Efficient SF is achieved through a high degree of interchromophoric coupling that facilitates electron super‐exchange to generate triplet pairs. Here we show that a predesigned chromophoric linker with extremely poor ISC efficiency ( k ISC ) but form triplets in MOF in contrast to the frameworks that are built from linkers with sizable k ISC but . This work opens a new photophysical and photochemical avenue in MOF chemistry and utility in energy conversion schemes.