Triplet-fusion-based photon upconversion holds promise for a wide range of applications, from photovoltaics to bioimaging. The efficiency of triplet fusion, however, is fundamentally limited in conventional molecular and polymeric systems by its spin dependence. Here, we show that the inherent tailorability of metal–organic frameworks (MOFs), combined with their highly porous but ordered structure, minimizes intertriplet exchange coupling and engineers effective spin mixing between singlet and quintet triplet–triplet pair states. We demonstrate singlet–quintet coupling in a pyrene-based MOF, NU-1000. An anomalous magnetic field effect is observed from NU-1000 corresponding to an induced resonance between singlet and quintet states that yields an increased fusion rate at room temperature under a relatively low applied magnetic field of 0.14 T. Our results suggest that MOFs offer particular promise for engineering the spin dynamics of multiexcitonic processes and improving their upconversion performance.

基于三重聚变的光子上转换有望用于从光伏到生物成像的广泛应用。然而，三重态融合的效率在传统分子和聚合物系统中因其自旋依赖性而受到根本限制。在这里，我们展示了金属有机骨架 (MOF) 固有的可定制性，结合它们高度多孔但有序的结构，最大限度地减少了三重态间交换耦合，并在单重态和五重态三重态-三重态对状态之间设计了有效的自旋混合。我们在基于芘的 MOF NU-1000 中展示了单重态-五重态耦合。从 NU-1000 观察到异常磁场效应，对应于单重态和五重态之间的感应共振，在 0.14 T 的相对较低的应用磁场下，在室温下产生增加的聚变率。