Developing stable gel materials for adsorption and catalysis is one of the major themes of gel materials. However, it has been proven to be challenging to achieve them from small molecules. Herein, an imine gel is developed from tetra-aldehyde 4-{2,2-bis[(4-formylphenoxy)methyl]-3-(4-formylphenoxy)propoxy}benzaldehyde (A4) and 3,3′-dihydroxybenzidine (B2) based on dynamic covalent chemistry. The unstable A4B2-imine gel is further converted into a stable aromatic benzoxazole-linked A4B2-benzoxazole gel via oxidative cyclization, which has significantly improved chemical stability under acidic and basic conditions. Benefiting from the stability under acidic conditions, the A4B2-benzoxazole gel is used for Pd(II) adsorption and the adsorption capacity is 250 mg g^–1. After PdCl₂ immersion and reduction, palladium nanoparticles with a size distribution of 1.3–14.7 nm are encapsulated by the network structure of the stable porous benzoxazole gel matrix. The Pd@A4B2-benzoxazole gel exhibits high catalytic activity toward the reduction of toxic hexavalent chromium Cr(VI) (reaction rate constant = 0.0377 min^–1), while there is no significant decrease in the catalytic efficiency after five cycles.

中文翻译：

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由亚胺凝胶合成稳定的苯并恶唑凝胶用于吸附和催化

开发用于吸附和催化的稳定的凝胶材料是凝胶材料的主要主题之一。然而，已经证明从小分子获得它们具有挑战性。在本文中，由四醛4- {2,2-双[（4-甲酰基苯氧基）甲基] -3-（4-甲酰基苯氧基）丙氧基}苯甲醛（A4）和3,3'-二羟基联苯胺（B2 ）基于动态共价化学。不稳定的A4B2-亚胺凝胶通过氧化环化作用进一步转变为稳定的芳族苯并恶唑连接的A4B2-苯并恶唑凝胶，这在酸性和碱性条件下具有显着改善的化学稳定性。得益于在酸性条件下的稳定性，A4B2-苯并恶唑凝胶可用于Pd（II）吸附，吸附容量为250 mg g ^–1。PdCl _2之后浸没和还原后，尺寸为1.3-14.7 nm的钯纳米颗粒被稳定的多孔苯并恶唑凝胶基质的网络结构包裹。Pd @ A4B2-苯并恶唑凝胶对有毒六价铬Cr（VI）的还原具有高催化活性（反应速率常数= 0.0377 min ^–1），而五个循环后催化效率没有明显降低。