The potential applications of metal–organic cages (MOCs) are mostly achieved through specific host–guest interactions within their cavities. Electronic applications would require an effective electron transport pathway, which has been extensively studied in hybrid organic–inorganic materials with extended structures. These properties have not been considered for MOCs because cage-to-cage interactions in these materials have rarely been examined and are challenging to functionalize. We report here a previously unobserved actinide-based MOC assembled from four hexagonal-bipyramidal-coordinated uranyl ions and six bidentate flexible ligands. Remarkably, each isolated cage is further interlocked with six adjacent ones through mechanical bonds, resulting in the first case of a 0D → 3D f-element polycatenated metal–organic cage, SCU-14. Long-range π–π stacking extending throughout the structure is built via polycatenation, providing a visible carrier transmission path. SCU-14 is also an extremely rare case of an intrinsically semiconductive MOC with a wide band gap of 2.61 eV. Combined with the high X-ray attenuation efficiency, SCU-14 can effectively convert X-ray photons to electrical current signals and presents a promising sensitivity of 54.93 μC Gy–1 cm–2.

Exciton behaviors including exciton formation and dissociation dynamics play an essential role in the optoelectronic performance of semiconductive materials but remain unexplored in semiconductive metal–organic frameworks (MOFs). Herein, we reveal that the exciton behaviors in semiconductive MOFs can be regulated by framework–guest interactions, a feature often not achievable in traditional inorganic or organic semiconductors. Incorporation of the electron-deficient molecule within the pores of a terbium-based semiconductive MOF (Tb2L2·4H2O·6DMF, L = TATAB3–, 4,4′,4″-s-triazine-1,3,5-triyltri-p-aminobenzoate, DMF = N,N-dimethylformamide) results in efficient energy transfer from the MOF skeleton to molecular acceptors, with a yield of up to 77.4%. This interaction facilitates distinctive exciton type conversion, giving rise to modified conductivity and photoelectric performance. We further fabricated a MOF-based X-ray detection device to demonstrate how the new architecture bolsters the optoelectronic efficiency, which outperforms the properties of parent semiconductive MOFs, with more than 60 times and 40 times enhancement of the photocurrent on–off ratio and detection sensitivity, respectively. With judiciously optimized exciton behaviors, the detection device exhibits a high sensitivity of 51.9 μC Gyair –1 cm–2 and records a charge carrier mobility-lifetime product of 1.12 × 10–3 cm2 V–1 among MOF-based X-ray detectors, which are competitive with values for commercially available detectors. These findings demonstrate a rational synthetic approach to designing exciton arrangements to improve the optoelectronic efficiency of semiconductive MOFs.

No abstract

We disclose the intrinsic semiconducting properties of one of the largest mixed-valent uranium clusters, [Single-crystal X-ray crystallography demonstrates that U V center is stabilized within a tetraoxo core surrounded by eight uranyl(VI) pentagonal bipyramidal centers. The oxidation states of uranium are substantiated by spectroscopic data and magnetic susceptibility measurement. Electronic spectroscopy and theory corroborate that U V species serve as electron donors and thus facilitate 1 being a n-type semiconductor. With the largest effective atomic number among all reported radiation-detection semiconductor materials, charge transport properties and photoconductivity were investigated under Xray excitation for 1: a large on-off ratio of 500 and considerable charge mobility lifetime product of 2.3 10 À4 cm 2 V À1 , as well as a high detection sensitivity of 23.4 mC Gy air À1 cm À2 .

For the first time, we are successful in preparing 2D MOF nanosheets in a monolayer manner via photo-exfoliation.