Mechanically Transformed ZIF-67 Phases as Catalytically Active Nanomaterials for Ammonia Borane Hydrolysis

Zeolitic imidazole frameworks (ZIFs) with tailored open metal sites hold great promise for catalysis. Ball milling of sodalite (SOD) ZIF-67 transformed a stable framework into metastable kat and dia ZIF-67 phases. These metastable phases showed catalytic activity for ammonia borane (AB) hydrolysis, transforming into a nano sheet-like cobalt–imidazolate catalyst ( nano Co-Im Cat, dimensions of 40–110 nm), featuring broken Co–N bonds and exposed Lewis acidic (Co 3+ /Co 2+ ) and basic (N) sites as a consequence of structural opening. The catalyst exhibited good activity; 3 equiv of H 2 was released within 2 min with an activation energy of 45.48 ± 0.97 kJ/mol, whereas pristine SOD ZIF-67 showed no detectable activity under identical conditions.