Enhanced Hydrolytic Stability of Self-Assembling Alkylated Two-Dimensional Covalent Organic Frameworks
Enhanced Hydrolytic Stability of Self-Assembling Alkylated Two-Dimensional Covalent Organic Frameworks
复制标题
DOI：
10.1021/ja203807h
复制
发表时间：
2011-09-07
影响因子：
15
通讯作者：
Lavigne, John J.
中科院分区：
文献类型：
--
作者：
Lanni, Laura M.;Tilford, R. William;Lavigne, John J.
研究了二维硼酸酯连接的共价有机骨架（COF）在水溶液中的稳定性和整体性质。与非烷基化的裸孔框架相比，在COF的孔中具有烷基化的框架观察到增强的稳定性。COF-18埃和COF-5被分析为“裸孔”COF，而COF-16埃（甲基）、COF-14埃（乙基）和COF-11埃（丙基）被评价为“烷基化孔”材料。在浸没在水性介质中时，烷基化的COF的孔隙率降低了约25%，而非烷基化的COF几乎完全水解，几乎失去了所有的孔隙率。对于这些材料的结晶度，观察到类似的趋势，烷基化COF降低40%，非烷基化COF降低95%。使用SEM来探测这些水解材料的粒度和形态。使用吸收光谱和（1）H NMR的稳定性试验监测了COF降解时单体的释放。虽然非烷基化的COF在有机溶剂中是稳定的，但水解在水性环境中是快速的，与中性或酸性水性介质相比，在碱性中更是如此（分别为几分钟至几小时）。值得注意的是，COF孔中的烷基化减缓了水解，表现出COF-11埃的稳定性比COF-18埃高50倍。
The stability and bulk properties of two-dimensional boronate ester-linked covalent organic frameworks (COFs) were investigated upon exposure to aqueous environments. Enhanced stability was observed for frameworks with alkylation in the pores of the COF compared to nonalkylated, bare-pore frameworks. COF-18 angstrom and COF-5 were analyzed as "bare-pore" COFs, while COF-16 angstrom (methyl), COF-14 angstrom (ethyl), and COF-11 angstrom (propyl) were evaluated as "alkylated-pore" materials. Upon submersion in aqueous media, the porosity of alkylated COFs decreased similar to 25%, while the nonalkylated COFs were almost completely hydrolyzed, virtually losing all porosity. Similar trends were observed for the degree of crystallinity for these materials, with similar to 40% decrease for alkylated COFs and 95% decrease for nonalkylated COFs. SEM was used to probe the particle size and morphology for these hydrolyzed materials. Stability tests, using absorbance spectroscopy and (1)H NMR, monitored the release of monomers as the COF degraded. While nonalkylated COFs were stable in organic solvent, hydrolysis was rapid in aqueous environments, more so in basic compared to neutral or acidic aqueous media (minutes to hours, respectively). Notably, alkylation in the pores of COFs slows hydrolysis, exhibiting up to a 50-fold enhancement in stability for COF-11 angstrom over COF-18 angstrom.