Soft porous coordination polymers [1] (SPCPs) are a new kind of porous materials composed of metal-organic polyhedra (MOP) and organic linkers. These novel adsorbents could combine the excellent properties of metal-organic frameworks (permanent porosity, high surface area and pore volume, low weight,
etc.) and soft materials (flexibility, processability, among others). As such, these materials have great potential in many areas of science and engineering (gas adsorption [2], hydrogen storage [3], carbon dioxide capture [4], methane storage [4], drug delivery [5], catalysis [6], sensors [7],
etc.). To advance technologies using SPCPs, fundamentals studies on structural properties and behavior are needed. It is known from experiments that SPCPs form amorphous structures but generating them by computational methods is very challenging. We use molecular modeling and simulations to design and generate the structures and calculate their structural properties. We employ different approaches to generate SPCPs by a) using an idealized crystalline structure and performing a compression/decompression scheme; and b) using the Amorphous Builder (Ambuild) [8] software. We characterize the systems by calculating surface area, pore volume, density, radial distribution function, pore size distribution, glass transition temperatures, among others. Also, we study the effects of chemistry, coordination, and linkers length and flexibility on the physical properties and gas adsorption performance. We also calculate the free energy as a function of the radius of gyration of SPCP to determine the different energy minima and explore the flexibility of the systems. From the calculations, we can see the different energy minima showing crystalline and amorphous metastable states. These characterizations are the first step towards leveraging the permanent porosity and flexible nature of these materials in adsorption applications.
References
1. Colón, Y. J. & Furukawa, S. Understanding the role of linker flexibility in soft porous coordination polymers. Mol. Syst. Des. Eng. 5, 284–293 (2020).
2. Herm, Z. R., Swisher, J. A., Smit, B., Krishna, R. & Long, J. R. MetalÀOrganic Frameworks as Adsorbents for Hydrogen Purification and Precombustion Carbon Dioxide Capture. J. Am. Chem. Soc 133, 5664–5667 (2011).
3. Bobbitt, N. S., Chen, J. & Snurr, R. Q. High-Throughput Screening of Metal−Organic Frameworks for Hydrogen Storage at Cryogenic Temperature. J. Phys. Chem. C 120, 48 (2016).
4.Lin, Y., Kong, C., Zhang, Q. & Chen, L. Metal-Organic Frameworks for Carbon Dioxide Capture and Methane Storage. Adv. Energy Mater. 7, 1601296 (2017).
5.Horcajada, P. et al. Metal–Organic Frameworks as Efficient Materials for Drug Delivery. Angew. Chemie Int. Ed. 45, 5974–5978 (2006).
6. Lee, J. et al. Metal-organic framework materials as catalysts. Chem. Soc. Rev. 38, 1450–1459 (2009).
7. Kreno, L. E. et al. Metal-organic framework materials as chemical sensors. Chemical Reviews vol. 112 1105–1125 (2012).
8. Thomas, J. M. H. et al. Artificial Synthesis of Conjugated Microporous Polymers via Sonogashira−Hagihara Coupling. (2020) doi:10.1021/acs.jpcb.0c04850.
