Gamma Ray Radiation Promotes Linker Mixing in Multivariate Metal-Organic Frameworks

Mixed-linker-based multivariate metal-organic frameworks (MTV-MOFs) recently received considerable research effort because they exhibit tailored physicochemical properties that are often not possessed by single-linker MOFs and therefore find unique applications. Relative to the pristine linker, the incorporated linkers may tend to form different topologies, bringing about lattice mismatch and structural disorder. This leads to a low mixed-linker incorporation limit, and further increasing the linker incorporation rate may disrupt the crystallinity of the parent MOF, resulting in amorphous products or other topologies. Therefore, increasing the linker incorporation rate without changing the structure of the parent MOF represents a challenge. Herein, for the first time, an MTV-MOF of imidazole-incorporated zeolitic imidazolate framework ZIF-7 is constructed by ⁶⁰Co gamma ray radiation. Both experiments and theoretic calculations demonstrate that the distinct radiation-induced activation of the synthesis reaction gives rise to a much higher mixed-linker incorporation limit in ZIF-7, up to twice that synthesized by the solvothermal process, further leading to increased flexibility of aperture, higher specific surface area, and notably enhanced separation performances for Kr and Xe. These observations suggest that radiation synthesis may emerge as a general route to a series of MTV-MOFs with significantly enhanced linker mixing limit and physicochemical properties.