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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) butform triplets in MOF in contrast to the frameworks that are built from linkers with sizablek_ISCbut. This work opens a new photophysical and photochemical avenue in MOF chemistry and utility in energy conversion schemes. 

Metal–organic frameworks (MOFs) have emerged as promising porous optoelectronic compositions for energy conversion and sensing applications. The enormous structural possibilities, the large variety of photo- and redox-active building blocks along with several post-synthetic functionalization strategies make MOFs an ideal platform for photochemical and photoelectrochemical developments. Because MOFs assemble all the active building units in a dense fashion, the non-aggregated yet proximally positioned species ensure efficient photon absorption to drive photoinduced charge transfer (PCT) reactions for energy conversion and sensing. Hence, understanding the PCT processes within MOFs as a function of the topological and electronic structures of the donor–acceptor (D–A) moieties can provide transformative strategies to design new low-density compositions.