In this work, the inclusion of free sulfonic acid groups in highly stable MOFs is explored. The synthesized catalysts have been applied in a model esterification reaction. Two metal organic frameworks bearing sulfonic acid moieties are investigated: HSO3-MIL-101(Cr) synthesized following different approaches and a new structure based on HSO3-bdc and Zr. The acidic properties, catalytic performance, deactivation and stability of the different structures are critically evaluated. In the case of MIL-101(Cr), deactivation of the sulfonic groups via formation of butanol sulfonic esters has been observed. Due to the strong interaction between âSO3â and the Cr open metal site where usually fluorine (Fâ) is located in the structure, the HSO3-MIL-101(Cr) catalysts are not stable under acidic regeneration conditions. When using Zr as a metal node, a new and stable sulfonic acid containing porous structure was synthesized. This structure showed high activity and full re-usability in the esterification of n-butanol with acetic acid. In this case, deactivation of the catalyst due to sulfonic ester formation could be reversed by reactivation under acidic conditions.
在这项研究中,探讨了在高度稳定的
金属有机框架(MOFs)中加入游离
磺酸基团的可能性。合成的催化剂已应用于一个模式酯化反应。研究了两种具有
磺酸基团的
金属有机框架:HSO3-MIL-101(Cr),采用不同的方法合成,以及基于HSO3-bdc和
锆的新结构。这些不同结构的酸性特性、催化性能、失活和稳定性进行了严格评估。在MIL-101(Cr)的情况下,观察到通过形成
丁醇磺酸酯导致
磺酸基团的失活。由于–SO3⁻与Cr开放
金属位点之间的强相互作用,而在该结构中,通通常位于该
金属位点的位置是
氟(F⁻),因此HSO3-MIL-101(Cr)催化剂在酸性再生条件下不稳定。当使用
锆作为
金属节点时,合成了一种新型且稳定的含
磺酸的多孔结构。该结构在
丁醇与
醋酸的酯化反应中表现出了高活性和完全可重用性。在这种情况下,由于
磺酸酯形成导致的催化剂失活可以通过在酸性条件下的再活化得以逆转。