Fluids under extreme confinement show characteristics significantly different from those of their bulk counterpart. This work focuses on water confined within the complex cavities of highly hydrophobic metal–organic frameworks (MOFs) at high pressures. A combination of high-pressure intrusion–extrusion experiments with molecular dynamic simulations and synchrotron data reveals that supercritical transition for MOF-confined water takes place at a much lower temperature than in bulk water, ∼250 K below the reference values. This large shifting of the critical temperature (T_c) is attributed to the very large density of confined water vapor in the peculiar geometry and chemistry of the cavities of Cu₂tebpz (tebpz = 3,3′,5,5′-tetraethyl-4,4′-bipyrazolate) hydrophobic MOF. This is the first time the shift of T_c is investigated for water confined within highly hydrophobic nanoporous materials, which explains why such a large reduction of the critical temperature was never reported before, neither experimentally nor computationally.

中文翻译：

---

疏水性金属有机框架中限制的温和超临界水


极端限制下的流体表现出与散装流体显着不同的特性。这项工作的重点是在高压下限制在高度疏水性金属有机框架（MOF）的复杂空腔内的水。高压侵入-挤出实验与分子动力学模拟和同步加速器数据相结合表明，MOF 约束水的超临界转变发生在比本体水低得多的温度下，比参考值低约 250 K。临界温度 (T _c ) 的这种大幅变化归因于 Cu ₂ tebpz (tebpz = 3,3',5,5'-四乙基-4,4'-联吡唑酯）疏水性 MOF。这是首次研究高度疏水性纳米多孔材料内限制的水的 T _c 变化，这解释了为什么之前从未报道过如此大的临界温度降低，无论是实验还是计算。