Department of Materials Science and Engineering, Peking University, Beijing 100871 (PR China).
Chemphyschem. 2014 Jan 13;15(1):126-31. doi: 10.1002/cphc.201300830. Epub 2013 Nov 29.
Phthalocyanine (Pc) molecules are well-known flexible structural units for 1D nanotubes and 2D nanosheets. First-principles calculations combined with grand canonical Monte Carlo simulations are used to obtain the geometries, electronic structures, optical properties, and hydrogen-storage capacities of nanocages consisting of six Pc molecules with six Mg or Ca atoms. The primitive Pc cage has Th symmetry with twofold degeneracy in the highest occupied molecular orbital (HOMO), and threefold degeneracy in the lowest unoccupied molecular orbital (LUMO); the corresponding HOMO-LUMO gap is found to be 0.97 eV. The MgPc and CaPc cages have Oh symmetry with a HOMO-LUMO gap of 1.24 and 1.13 eV, respectively. Optical absorption spectra suggest that the Pc-based cages can absorb infrared light, which is different from the visible-light absorption in Pc molecules. We further show that the excess uptake of hydrogen on MgPc and CaPc cages at 298 K and 100 bar (1 bar=0.1 MPa) is about 3.49 and 4.74 wt%, respectively. The present study provides new insight into Pc-based nanostructures with potential applications.
酞菁（Pc）分子是一维纳米管和二维纳米片的知名柔性结构单元。我们采用第一性原理计算结合巨正则蒙特卡罗模拟，得到了由六个 Pc 分子和六个 Mg 或 Ca 原子组成的纳米笼的几何形状、电子结构、光学性质和储氢能力。原始的 Pc 笼具有 Th 对称性，在最高占据分子轨道（HOMO）中具有两倍简并，在最低未占据分子轨道（LUMO）中具有三倍简并；相应的 HOMO-LUMO 能隙为 0.97eV。MgPc 和 CaPc 笼具有 Oh 对称性，HOMO-LUMO 能隙分别为 1.24 和 1.13eV。光学吸收光谱表明，基于 Pc 的笼可以吸收红外光，这与 Pc 分子中的可见光吸收不同。我们进一步表明，在 298K 和 100 巴（1 巴=0.1MPa）下，MgPc 和 CaPc 笼对氢气的过量吸收分别约为 3.49wt%和 4.74wt%。本研究为具有潜在应用的基于 Pc 的纳米结构提供了新的见解。
