There is a lack of water sorbents capable of cycling water vapor under dry conditions without hysteresis or decomposition. Here, the authors demonstrate that the anionic MOF SU-102 exhibits high-capac...

Increasing the connectivity of structural units presents a potentially valuable approach to improve hydrolytic stability in metal–organic frameworks (MOFs). We herein leverage this strategy by synthesizing the first tritopic benzotriazolate MOF, Zn5(OAc)4(TBTT)2 (H3TBTT = 2,4,6-tris(1H-benzo[d][1,2,3]triazol-5-yl)-1,3,5-triazine), which exhibits open metal sites, high connectivity, high porosity, and significant water uptake capacity. The MOF adopts a previously unknown topology with (3,6,6)-connectivity, which is supported by single-crystal electron diffraction and elemental analysis. The framework undergoes postsynthetic metal and anion exchange with NiCl2, which increases the accessible pore volume and the net hydrophilicity of the framework. With this exchange, the apparent BET surface area increases from 1994 to 3034 m2/g, and the water uptake step shifts from 56 to 33% relative humidity (RH). The high gravimetric capacity of the Ni-rich MOF, 0.98 g/g, translates to a working capacity of 0.64 g/g during a pressure swing cycle between 20 and 40% RH at 25 °C. Combining this performance with a less than 2% loss in working capacity over 100 cycles, the new material rivals the best MOF water sorbents to date.

Sodium-ion batteries (SIBs) attract significant attention due to their potential as an alternative energy storage solution, yet challenges persist due to the limited energy density of existing cathode materials. In principle, redox-active organic materials can tackle this challenge because of their high theoretical energy densities. However, electrode-level energy densities of organic electrodes are compromised due to their poor electron/ion transport and severe dissolution. Here, we report the use of a low-bandgap, conductive, and highly insoluble layered metal-free cathode material for SIBs. It exhibits a high theoretical capacity of 355 mAh g–1 per formula unit, enabled by a four-electron redox process, and achieves an electrode-level energy density of 606 Wh kg–1electrode (90 wt % active material) along with excellent cycling stability. It allows for facile two-dimensional Na+ diffusion, which enables a high intrinsic rate capability. Growth of the active cathode material in the presence of as little as 2 wt % carboxyl-functionalized carbon nanotubes improves charge transport and charge transfer kinetics and further enhances the power performance. Altogether, these allow the construction of SIB cells built from an affordable, sustainable organic small molecule, which provide a cathode energy density of 472 Wh kg–1electrode when charging/discharging in 90 s and a top specific power of 31.6 kW kg–1electrode.

Mixed ionic-electronic conductors have great potential as materials for energy storage applications. However, despite their promising properties, only a handful of metal–organic frameworks (MOFs) prov...