A general and green approach of pH-sensitive ZIF-67 for encapsulating active substances

Zeolitic imidazolate framework-67 (ZIF-67) has emerged as a promising carrier for active substances (AS) due to its biocompatibility and acid-triggered degradation behavior. Conventional loading strategies often involve multi-step post-synthetic modifications or one-pot processes employing toxic organic solvents. This study presents a facile one-pot synthesis method for encapsulating AS into ZIF-67 in deionized water within 2 h under ambient conditions. This method exhibits broad applicability, enabling effective encapsulation of both hydrophobic and hydrophilic molecules with molecular weights ranging from low to high, with loading efficiencies between 12.17% and 56.11%. While free compounds were released rapidly in a pH-independent manner, both CA@ZIF-67 and EGCG@ZIF-67 proved pH-responsive sustained release profiles, with their mechanisms best described by the first-order model and Fickian diffusion, respectively. Moreover, these composites demonstrated synergistic and pH-dependent antibacterial activity against Escherichia coli and Staphylococcus aureus, showing significantly enhanced efficacy in acidic conditions. Furthermore, the formation process, morphological evolution, and release behavior of AS@ZIF-67 composites were elucidated through Monte Carlo simulations, modified attachment energy theory, and molecular dynamics simulations. This green one-pot strategy offers a versatile platform for applications in controlled release, antimicrobial systems, and targeted delivery.