Dr. Kate Lawrence, Editor for ChemPhysChem and ChemElectroChem, talks to Professor Qiang Sun about his article that has recently been accepted for publication in ChemPhysChem.

Professor Sun, you have explored the electronic structures, optical properties, and hydrogen-storage capabilities of phthalocyanine (Pc)-based nanocages by using a multi-scale modeling approach. What was the inspiration behind this study?

Tremendous attention has been paid to Pc-based 1D nanotubes and 2D nanosheets. However, until now, no study has been reported for Pc-based 0D nanocages. It has been reported in Nature Chemistry that the graphene sheet can not only form a carbon nanotube but also can form a fullerene cage. Following this logic, for the first time, we explored Pc-based nanocages.

What is the main significance of your results?

Compared with the cage of C₆₀, our studied Pc-based cage has the following features:

i) The cage is porous, so larger molecules can be easily encapsulated.

ii) The cage radius is twice of that of C₆₀ and the volume is eight times of that of C₆₀; therefore, the storage capacity is significantly improved.

iii) Owing to the smaller HOMO–LUMO gap, Pc-based cages can absorb light with larger wavelengths, so it can be photosensitized or photomanipulated for biomedical applications. Our work not only bridges the knowledge gap regarding 0D Pc-based nanostructures, but also provides possibilities for applications in energy conversion, drug storage, and gas separation.

Why was your attention focused on these types of materials?

One of the projects in our research group is to study porous organometallic materials for energy and the environment. Our previous studies have shown that the metal atoms in porous organometallic materials can be uniformly distributed in the substrate without clustering, and can display well-defined geometries and magnetic properties for potential applications in spintronics, hydrogen storage, and CO₂ capture. Our current attention is focused on further exploring the various allotropes, of different dimensions, that can be derived from the Pc-based sheet.

How long do you think it will be before this theoretical result becomes a reality?

The existing study has already shown that fullerene cages can be synthesized from graphene sheets, but we are not sure how long it will take to synthesize a Pc-based cage from the 2D sheet or from Pc molecules. We are more than happy to see the new progress in this field.

What is the broader impact of this paper for the scientific community?

This work should motivate people to develop new techniques for synthesizing and characterizing Pc-based porous cages, going beyond fullerenes, for unprecedented applications.

How will you follow up on this discovery?

In future work, we will concentrate on studying Pc-cage-based 3D materials, and Pc-cage-based devices for different applications.

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The article they talked about:

• Phthalocyanine-Based Organometallic Nanocages: Properties and Gas-Storage Capabilities,
  Guizhi Zhu, Yawei Li, Kun Lü, Qiang Sun,
  ChemPhysChem 2013.
  DOI: 10.1002/cphc.201300830

References for further reading:

• article mentioned in question 1:

  Direct transformation of graphene to fullerene,
  Andrey Chuvilin, Ute Kaiser, Elena Bichoutskaia, Nicholas A. Besley, Andrei N. Khlobystov,
  Nature Chem. 2010, 2, 450–453.
  DOI: 10.1038/nchem.644

• article on previous studies
  
  Magnetism of Phthalocyanine-Based Organometallic Single Porous Sheet,
  Jian Zhou, Qiang Sun
  J. Am. Chem. Soc. 2011, 133, 15113–15119.
  DOI: 10.1021/ja204990j

  Absorption induced modulation of magnetism in two-dimensional metalphthalocyanine porous sheets,
  Jian Zhou and Qiang Sun
  J. Chem. Phys. 2013, 138, 204706.
  DOI: 10.1063/1.4807016

  Strain-Induced Spin Crossover in Phthalocyanine-Based Organometallic Sheets,
  Jian Zhou, Qian Wang, Qiang Sun et al.,
  J. Phys. Chem. Lett. 2012, 3, 3109−3114.
  DOI: 10.1021/jz4017848
  

  Carrier induced magnetic coupling transitions in phthalocyanine-based organometallic sheet,
  Jian Zhou, Qiang Sun,
  Nanoscale 20.
  DOI: 10.1039/c3nr04041k

  Sc-phthalocyanine sheet: Promising material for hydrogen storage,
  Kun Lü, Jian Zhou, Le Zhou, Qian Wang, Qiang Sun, Puru Jena,
  Appl. Phys. Lett. 2011, 99, 163104–163103.
  DOI: 10.1063/1.3653465

  Pre-combustion CO₂ capture by transition metal ions embedded in phthalocyanine sheets,
  Kun Lü, Jian Zhou, Le Zhou , X. S. Chen, Siew Hwa Chan, Qiang Sun,
  J. Chem. Phys. 2012, 136, 234703–234707.
  DOI: 10.1063/1.4729471