Merchiori Sebastiano, Donne Andrea Le, Bhatia Ribhu, Alvelli Marta, Yu Jiang-Jing, Wu Xu-Dong, Li Mian, Li Dan, Scheller Lukasz, Lowe Alexander R, Geppert-Rybczynska Monika, Trump Benjamin A, Yakovenko Andrey A, Chorążewski Mirosław, Zajdel Paweł, Grosu Yaroslav, Meloni Simone
Department of Chemical, Pharmaceutical and Agricultural Sciences, University of Ferrara, Ferrara, 44121, Italy.
College of Chemistry and Chemical Engineering, Chemistry and Chemical Engineering Guangdong Laboratory, Shantou University, Guangdong, 515063, China.
Small. 2024 Oct;20(42):e2402173. doi: 10.1002/smll.202402173. Epub 2024 Aug 7.
Liquid porosimetry experiments reveal a peculiar trend of the intrusion pressure of water in hydrophobic Cu(3,3',5,5'-tetraethyl-4,4'-bipyrazolate) MOF. At lower temperature (T) range, the intrusion pressure (P) increases with T. For higher T values, P first reaches a maximum and then decreases. This is at odds with the Young-Laplace law, which for systems showing a continuous decrease of contact angle with T predicts a corresponding reduction of the intrusion pressure. Though the Young-Laplace law is not expected to provide quantitative predictions at the subnanoscale of Cu(tebpz) pores, the physical intuition suggests that to a reduction of their hydrophobicity corresponds a reduction of the P. Molecular dynamics simulations and sychrothron experiments allowed to clarify the mechanism of the peculiar trend of P with T. At increasing temperatures the vapor density within the MOF' pores grows significantly, bringing the corresponding partial pressure to ≈5 MPa. This pressure, which is consistent with the shift of P observed in liquid porosimetry, represents a threshold to be overcame before intrusion takes place. Beyond some value of temperature, the phenomenon of reduction of hydrophobicity (and water surface tension) dominated over the opposite effect of increase of vapor pressure and P inverts its trend with T.
液体孔隙率测定实验揭示了水在疏水性铜（3,3',5,5'-四乙基-4,4'-联吡唑）金属有机框架中的侵入压力呈现出一种奇特的趋势。在较低温度（T）范围内，侵入压力（P）随T升高。对于较高的T值，P首先达到最大值，然后下降。这与杨-拉普拉斯定律相悖，该定律对于接触角随T持续减小的系统预测侵入压力会相应降低。尽管预计杨-拉普拉斯定律在铜（tebpz）孔隙的亚纳米尺度上无法提供定量预测，但从物理直觉来看，疏水性降低应该对应着P的降低。分子动力学模拟和同步加速器实验有助于阐明P随T变化的奇特趋势的机制。随着温度升高，金属有机框架孔隙内的蒸汽密度显著增加，使相应的分压达到约5兆帕。这个压力与液体孔隙率测定中观察到的P的变化一致，代表了侵入发生前需要克服的一个阈值。超过某个温度值后，疏水性降低（以及水表面张力降低）的现象超过了蒸汽压增加的相反效应，P随T的趋势发生反转。
