Solid polymer electrolytes (SPEs) are crucial indevelopinglithium metal batteries. Recently, metal-organic frameworks (MOFs) with open metal sites (OMSs) have shown promise as solid fillers to improve the performance of SPEs. However, the number of OMSs-containing MOFs is quite limited, comprising less than 5% of the total MOFs.

Inthis research work,quasi-metalorganic frameworks (QMOFs) rich in OMSs were constructed by partially broken coordination bonds within the periodic MOF under controlled heat treatment. Taking the typical cobalt-based MOF (ZIF-67) as an example, aquasi-MOF(QZIF) was constructed by controlled heat treatment underargon protection. (Figure 1). Electron paramagnetic resonance, X-ray photoelectron spectroscopy, and Synchrotron X-ray absorption spectroscopy techniques verified that the constructed QZIF successfully exposed OMS with a Co-N coordination of 3.4. Density functional theory calculations and experimental results proved that the synthesized QZIFcouldadsorb anions in lithium salts and increase the Li⁺transference number.In addition, QZIF promoted the construction of a solid electrolyte interface (SEI) rich in LiF/Li₃N, which was beneficial to stabilize the electrolyte/electrode interface and inhibit the growth of lithium dendrites.

This work was supported by the National Natural Science Foundation of China, the Shenzhen Science and Technology Program, etc. The article is available from https://doi.org/10.1002/anie.202416170.

Figure 1.Design principle of quasi-MOF. a, Illustration of the design of quasi-MOF. b, Synthesis and coordination structure of ZIF-67 and QZIF. c, Simplified models about adsorption configuration of TFSI^-on CoN₄(ZIF-67) and CoN₂(QZIF) and the corresponding differential charge density. Green and yellow areas denoted the charge density decrease  (Δ𝜌 < 0) and increase (Δ𝜌 > 0), respectively.