Ma Zhiheng, Zhang Yu, Yuan Tongwei, Fan Yu, Wang Xiaowu, Xue Zhenggang, Zhong Aihua, Xu Jiaqiang
NEST Lab., Department of Chemistry, College of Science, Shanghai University, 99 Shangda Road, Shanghai 200444, China; Shenzhen Key Laboratory of Advanced Thin Films and Applications, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
NEST Lab., Department of Chemistry, College of Science, Shanghai University, 99 Shangda Road, Shanghai 200444, China.
J Hazard Mater. 2025 Mar 15;486:136859. doi: 10.1016/j.jhazmat.2024.136859. Epub 2024 Dec 17.
It is well known that metals and metal oxides with different crystal facets exhibit varying sensitivity in gas sensors, but this strategy is rarely used in metal-organic frameworks (MOFs). Herein, we proved for the first time that Cu metal-organic with high energy crystal facets (Cu-MOF-74-300) shows a much higher sensitivity than the low energy crystal facets (Cu-MOF-74-110), with a up to 2 times response more than Cu-MOF-74-110 and ultra-low limit of detection (LOD) of 68 ppb to toluene vapors. In addition, this strategy was further demonstrated on MOF-14 and HKUST-1, which are also Cu-centered and exhibit clear recognition effects on benzene and xylene, respectively. Furthermore, the Cu-MOF-74-300 shows high selectivity (92 %) and excellent stability, with a minor reduction in response of less than 1.9 % after 6 months. Additionally, the sensitive mechanism is explored by DFT and GCMC methods. The simulations reveal that Cu-MOF-74 includes two adsorption sites, one is Cu site with adsorption enthalpy (ΔH) of -59.04 kJ/mol, another is the benzene ring site (ΔH is -67.50 kJ/mol) in the ligand. The difference in charge densities reveal that the Cu and benzene ring on the surface of Cu-MOF-74-300 enables synergistic sensing, leading to more electron transfer in toluene than that of Cu-MOF-74-110 (only benzene ring site). Finally, based on the temperature-varying experiments, the experimental adsorption energy (-51.35 kJ/mol) was obtained by calculations. Combined quasi-in-situ XPS, implying Cu is the critical role to the improvement of Cu-MOF-74-300 sensitivity to toluene.
众所周知，具有不同晶面的金属和金属氧化物在气体传感器中表现出不同的灵敏度，但这种策略在金属有机框架（MOF）中很少使用。在此，我们首次证明，具有高能晶面的铜金属有机框架（Cu-MOF-74-300）比低能晶面（Cu-MOF-74-110）表现出更高的灵敏度，对甲苯蒸汽的响应比Cu-MOF-74-110高2倍，检测限低至68 ppb。此外，该策略在同样以铜为中心的MOF-14和HKUST-1上得到进一步验证，它们分别对苯和二甲苯表现出明显的识别效果。此外，Cu-MOF-74-300具有高选择性（92%）和出色的稳定性，6个月后响应仅轻微降低不到1.9%。此外，通过密度泛函理论（DFT）和巨正则蒙特卡罗（GCMC）方法探索了敏感机制。模拟结果表明，Cu-MOF-74包含两个吸附位点，一个是吸附焓（ΔH）为-59.04 kJ/mol的铜位点，另一个是配体中的苯环位点（ΔH为-67.50 kJ/mol）。电荷密度的差异表明，Cu-MOF-74-300表面的铜和苯环实现了协同传感，导致甲苯中的电子转移比Cu-MOF-74-110（只有苯环位点）更多。最后，基于变温实验，通过计算得到实验吸附能为-51.35 kJ/mol。结合准原位X射线光电子能谱（XPS），表明铜是提高Cu-MOF-74-300对甲苯灵敏度的关键因素。
