pK(a) -Directed Incorporation of Phosphonates into MOF-808 via Ligand Exchange: Stability and Adsorption Properties for Uranium
pK(a) -Directed Incorporation of Phosphonates into MOF-808 via Ligand Exchange: Stability and Adsorption Properties for Uranium
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pK(a) - 通过配体交换将磷酸盐直接掺入 MOF-808：铀的稳定性和吸附性能
DOI：
10.1021/acsami.9b10920
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发表时间：
2019
影响因子：
9.5
通讯作者：
Chen Jing
中科院分区：
文献类型：
--
作者：
Zhang Wen;Bu An;Ji Qingyuan;Min Luofu;Zhao Song;Wang Yuxin;Chen Jing
我们报道了一类pka定向的，通过配体交换将磷酸盐配体精确结合到锆基金属有机骨架（Zr-MOF） MOF-808中。通过甲基膦酸（MPA）、乙膦酸（EPA）和乙烯膦酸（VPA）取代MOF-808中略高于苯三羧酸（BTC）连接体的甲酸配体，可以在不控制MPA化学计量量的情况下合成子mof。甲基膦酸mof （808-MPAs）具有较高的孔隙率，与母体MOF-808相比，其孔径和比表面积变化很小。PXRD图谱和结构改进表明，在用甲基膦酸盐配体修饰后，所有mof的晶格都扩大了。XPS光谱显示配体交换后zr6节点的电荷重新分布。FTIR和31p MAS NMR结合DFT计算表明，甲基膦酸盐配体以CH3P(O)(OZr)（OH）的形式连接到zr6节点上，具有可接近的酸性P-OH基团。808-MPAs在浓HCl、浓HNO3、热水和0.2 mol/L三氟乙酸溶液中均表现出良好的化学稳定性。令人印象深刻的是，808-MPAs利用其腔环境中P-OH位点的离子交换特性，对铀酰离子表现出超快的吸附性能，其平衡时间为10 min，比以前的吸附剂快得多。本研究展示了一系列具有可调谐磷酸盐端配体的pka定向zr - mof的重要概念验证示例，这可以在不久的将来扩展到其他磷酸盐功能化的基于zr的框架平台。
We report a class of pKa-directed, precise incorporation of phosphonate ligands into a zirconium-based metal–organic framework (Zr-MOF), MOF-808, via ligand exchange. By replacing of formate ligands with methylphosphonic acid (MPA), ethanephosphonic acid (EPA), and vinylphosphonic acid (VPA), whose pKavalues are slightly higher than that of the benzenetricarboxylic acid (BTC) linker in MOF-808, daughter MOFs can be synthesized without controlling the stoichiometric amounts of added MPA. The methylphosphonate MOFs (808-MPAs) demonstrate high porosities, with only small changes in the pore diameter and specific surface area when compared with the parent MOF-808. PXRD patterns and structure refinements indicate the expansion of the lattice for all MOFs after decorating with methylphosphonate ligands. The XPS spectra reveal a charge redistribution of the Zr6node after ligand exchange. FTIR and31P MAS NMR spectra, combined with DFT calculation, suggest that the methylphosphonate ligand is connected to the Zr6node as CH3P(O)(OZr)(OH) species with an accessible acidic P–OH group. Besides, 808-MPAs demonstrate excellent chemical stability in concentrated HCl, concentrated HNO3, hot water, and 0.2 mol/L trifluoroacetic acid solutions. Impressively, 808-MPAs show ultrafast adsorption performance for uranyl ions using the ion-exchange property of P–OH sites in their cavity environment, with an equilibrium time of 10 min, much quicker than the previous adsorbents. The present study demonstrates a series of important proof-of-concept examples of the pKa-directed Zr-MOFs with tunable phosphonate-terminated ligands, which can extend to other phosphonate-functionalized Zr-based framework platforms in the near future.