Non-Isothermal Kinetics of Kr Adsorption by Nanoporous γ‑Mg(BH₄)₂ from in Situ Synchrotron Powder Diffraction

Crystalline materials with pore dimensions comparable to the kinetic diameters of the guest molecules are attractive for their potential use in adsorption and separation applications. The nanoporous γ-Mg­(BH4)2 features one-dimensional channels matching this criterion for Kr uptake, which has been probed using synchrotron powder diffraction at various pressures and temperatures. It results in two coexisting crystalline phases with the limiting composition Mg­(BH4)2·0.66Kr expecting the highest Kr content (50.7 wt % in the crystalline phase) reported for porous materials. Quasi-equilibrium isobars built from Rietveld refinements of Kr site occupancies were rationalized with a noncooperative lattice gas model, yielding the values of the thermodynamic parameters. The latter were independently confirmed from Kr fluorescence. We have also parameterized the pronounced kinetic hysteresis with a modified mean-field model adopted for the Arrhenius kinetics.孔径尺寸与客体分子动力学直径相当的晶体材料，因其在吸附与分离领域的潜在应用价值而具有显著吸引力。纳米多孔γ-二硼氢化镁(γ-Mg(BH₄)₂)拥有契合该标准的一维孔道，适用于氪气吸附，相关机制已通过不同压强与温度下的同步辐射粉末衍射进行了探究。研究结果表明体系中存在两种共存晶相，其极限组成为Mg(BH₄)₂·0.66Kr，该晶相的氪含量可达50.7 wt%，为多孔材料领域已报道的最高氪负载量。基于氪气孔点占有率的里特维尔德精修结果构建准平衡等压线，并通过非协作格子气体模型对其进行合理化阐释，得到了对应的热力学参数。上述热力学参数通过氪荧光实验得到了独立验证。此外，我们采用适配阿伦尼乌斯动力学的修正平均场模型，对显著的动力学滞后现象完成了参数化表征。