Preparation of Metal-Organic Framework-Gelatin Hydrogels Through Coacervation

An original and reproducible strategy is presented for the synthesis of green and environmentally benign gelatin-Zr(IV) Metal-Organic Framework (MOF) hydrogel composites, and is described in a step-by-step manner throughout the article. The approach exploits the thermo-reversible nature of gelatin and its ability to undergo phase separation through coacervation, combined with the in situ formation of UiO-66-type MOFs under mild conditions. Using this methodology, the present work demonstrates the preparation of a bionanocomposite based on gelatin and the chemically stable Zr⁴⁺ dicarboxylate UiO-66 MOF. Importantly, this strategy can be extended to a broader family of Zr(IV) dicarboxylate and fumarate MOFs (UiO-66-type MOFs and MOF-801, respectively), selected to span a wide range of hydrophilic-hydrophobic balance and organic linker functionalizations. The resulting hydrogel composites display key features such as high MOF loadings (exceeding 50 wt%), high accessible porosity, and a homogeneous dispersion of MOF nanoparticles within the gelatin network. These properties arise from the strong interfacial compatibility between gelatin and MOF nanoparticles, as evidenced by complementary advanced characterization techniques. Owing to their robust mechanical behavior under ambient conditions, the composites can be processed at the gram scale into various macroscopic forms, such as coatings or monoliths, enabling their use in diverse applications, including the capture or catalytic conversion of pollutants in water or air under ambient conditions.