Coordination-Enabled One-Step Assembly of Ultrathin, Hybrid Microcapsules with Weak pH-Response

In this study, an ultrathin, hybrid microcapsule is prepared though coordination-enabled one-step assembly of tannic acid (TA) and titanium(IV) bis(ammonium lactate) dihydroxide (Ti-BALDH) upon a hard-templating method. Briefly, the PSS-doped CaCO3 microspheres with a diameter of 5–8 μm were synthesized and utilized as the sacrificial templates. Then, TA-TiIV coatings were formed on the surface of the PSS-doped CaCO3 templates through soaking in TA and Ti-BALDH aqueous solutions under mild conditions. After removing the template by EDTA treatment, the TA-TiIV microcapsules with a capsule wall thickness of 15 ± 3 nm were obtained. The strong coordination bond between polyphenol and TiIV conferred the TA-TiIV microcapsules high structural stability in the range of pH values 3.0–11.0. Accordingly, the enzyme-immobilized TA-TiIV microcapsules exhibited superior pH and thermal stabilities. This study discloses the formation of TA-TiIV microcapsules that are suitable for use as supports in catalysis due to their extensive pH and thermal stabilities.