Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China.
Phys Chem Chem Phys. 2018 Jul 11;20(27):18192-18199. doi: 10.1039/c8cp00466h.
Single-layer membranes of porous graphene, graphyne derivatives (α/α2/β-graphyne), and porous boron nitride (BN) with similar pore sizes (approximately 8 × 6 Å) have been evaluated for separating pentane isomers using first-principles calculations. In spite of their slightly bigger pore sizes, graphyne derivatives only allow linear pentane molecules to go through their native pores, while in contrast porous graphene and BN membranes only block dibranched isomers, i.e., neopentane molecules. Analyses of the geometric changes reveal that the structural flexibility of the membrane determines the penetration barrier. During the penetration of molecules, rigid membranes like graphyne derivatives may exhibit similar distortion to flexible porous graphene and BN; however the energy increase for the former is twice that for the latter. More importantly, the passing molecules experience about two times geometry distortion and four times energy barrier increase when going through rigid membranes compared with flexible membranes. The more deformed passing molecule and the less deformed rigid membrane can result in a much higher penetration barrier. Our results show that the flexibility of porous BN is comparable to that of porous graphene while graphyne derivatives are much more rigid.
使用第一性原理计算，我们评估了具有相似孔径（约 8×6Å）的多孔石墨烯、石墨炔衍生物（α/α2/β-石墨炔）和多孔氮化硼（BN）单层膜对戊烷异构体的分离性能。尽管石墨炔衍生物的孔径稍大，但只有线性戊烷分子可以通过其本征孔，而相反，多孔石墨烯和 BN 膜只能阻挡支链异构体，即新戊烷分子。通过对几何变化的分析发现，膜的结构灵活性决定了渗透势垒。在分子渗透过程中，像石墨炔衍生物这样的刚性膜可能会表现出与柔性多孔石墨烯和 BN 相似的变形；然而，前者的能量增加是后者的两倍。更重要的是，与柔性膜相比，刚性膜中通过的分子经历约两倍的几何变形和四倍的能量势垒增加。通过的分子变形越大，刚性膜的变形越小，渗透势垒就越高。我们的结果表明，多孔 BN 的灵活性可与多孔石墨烯相媲美，而石墨炔衍生物则更刚性。
