Adaptive Discovery of Uncharted Zeolitic Imidazolate Frameworks

Discovering new zeolitic imidazolate framework (ZIF) structures remains a major challenge because their assembly depends on the nature of the linker and synthesis conditions. Here, we introduce linker width as a design parameter for ZIF synthesis. We designed 4-substituted benzimidazole linkers with expanded width and combined them with smaller linkers in an adaptive machine-learning (ML) high-throughput strategy. This adaptive discovery scheme yielded nine new mixed-linker ZIFs, including six adopting the previously unrealized bcv topology. Single-crystal structural analysis reveals ordered linker distributions in which the wider 4-substituted benzimidazolate linkers code for the formation of 10-membered-ring needed for the apertures of the bcv cage. Comparison with representative mixed-linker ZIFs further identifies the width of linkers and the extension ratio as steric descriptors of topology selection. These results provide chemically interpretable design principles for mixed-linker ZIF assembly and demonstrate how linker design coupled with ML-guided synthesis can access unexplored regions of chemical space.