Attallah Ahmed G, Bon Volodymyr, Maity Kartik, Zaleski Radosław, Hirschmann Eric, Kaskel Stefan, Wagner Andreas
Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
Physics Department, Faculty of Science, Minia University, P.O. 61519, Minia, Egypt.
J Phys Chem Lett. 2024 May 2;15(17):4560-4567. doi: 10.1021/acs.jpclett.4c00762. Epub 2024 Apr 19.
Metal-organic frameworks (MOFs) stand as pivotal porous materials with exceptional surface areas, adaptability, and versatility. Positron Annihilation Lifetime Spectroscopy (PALS) is an indispensable tool for characterizing MOF porosity, especially micro- and mesopores in both open and closed phases. Notably, PALS offers porosity insights independent of probe molecules, which is vital for detailed characterization without structural transformations. This study explores how metal ion states in MOFs affect PALS results. We find significant differences in measured porosity due to paramagnetic or metal ions compared to simulated values. By analyzing CPO-27(M) (M = Mg, Co, Ni), with identical pore dimensions, we observe distinct PALS data alterations based on metal ions. Paramagnetic Co and Ni ions hinder and quench positronium (Ps) formation, resulting in smaller measured pore volumes and sizes. Mg only quenches Ps, leading to underestimated pore sizes without volume distortion. This underscores the metal ions' pivotal role in PALS outcomes, urging caution in interpreting MOF porosity.
金属有机框架材料（MOFs）是一类关键的多孔材料，具有出色的比表面积、适应性和多功能性。正电子湮没寿命谱（PALS）是表征MOF孔隙率的不可或缺的工具，尤其适用于开放和封闭相中微孔和介孔的表征。值得注意的是，PALS提供的孔隙率信息独立于探针分子，这对于在不发生结构转变的情况下进行详细表征至关重要。本研究探讨了MOFs中的金属离子状态如何影响PALS结果。我们发现，与模拟值相比，顺磁性或金属离子导致测量的孔隙率存在显著差异。通过分析具有相同孔径的CPO-27（M）（M = Mg、Co、Ni），我们观察到基于金属离子的不同PALS数据变化。顺磁性Co和Ni离子阻碍并猝灭了正电子素（Ps）的形成，导致测量的孔体积和尺寸较小。Mg仅猝灭Ps，导致孔径被低估但体积无畸变。这突出了金属离子在PALS结果中的关键作用，提醒在解释MOF孔隙率时要谨慎。
