From Molecules to Materials: Computational Design of N-Containing Porous Aromatic Frameworks for CO2Capture

Porous Aromatic Frameworks (PAFs)

Porous aromatic frameworks (PAFs) represent an important category of porous solids. PAFs possess rigid frameworks and exceptionally high surface areas, and, uniquely, they are constructed from carbon-carbon-bond-linked aromatic-based building units. Various functionalities can either originate from the intrinsic chemistry of their building units or are achieved by postmodification of the aromatic motifs using established reactions. Specially, the strong carbon-carbon bonding renders PAFs stable under harsh chemical treatments. Therefore, PAFs exhibit specificity in their chemistry and functionalities compared with conventional porous materials such as zeolites and metal organic frameworks. The unique features of PAFs render them being tolerant of severe environments and readily functionalized by harsh chemical treatments. The research field of PAFs has experienced rapid expansion over the past decade, and it is necessary to provide a comprehensive guide to the essential development of the field at this stage. Regarding research into PAFs, the synthesis, functionalization, and applications are the three most important topics. In this thematic review, the three topics are comprehensively explained and aptly exemplified to shed light on developments in the field. Current questions and a perspective outlook will be summarized.

Microwave-assisted synthesis of high thermal stability and colourless polyimides containing pyridine

A novel aromatic diamine containing pyridyl side group, 4-pyridine-4,4-bis(3,5-dimethyl-5-aminophenyl)methane (PyDPM), was successfully synthesized via electrophilic substitution reaction. The polyimides (PIs) containing pyridine were obtained via the microwave-assisted one-step polycondensation of the PyDPM with pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenylether tetracarboxylic dianhydride (ODPA) and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). Contrarily to the reported similar PIs, these PIs exhibit much higher thermal stability or heat resistance, i.e. high glass transition temperatures (T gs) in the range of 358-473°C, and the decomposition temperatures at 5% weight loss over 476°C under nitrogen. They can afford flexible and strong films with tensile strength of 82.1-93.3 MPa, elongation at break of 3.7%-15.2%, and Young's modulus of 3.3-3.8 GPa. Furthermore, The PI films exhibit good optical transparency with the cut-off wavelength at 313-366 nm and transmittance higher than 73% at 450 nm. The excellent thermal and optical transmittance can be attributed to synthesis method and the introduction of pyridine rings and ortho-methyl groups. The inherent viscosities of PIs via one-step method were found to be 0.58-1.12 dl g-1 in DMAc, much higher than those via two-step method. These results indicate these PIs could be potential candidates for optical substrates of organic light emitting diodes (OLEDs).

High and Selective Carbon Dioxide Capture in Nitrogen-Containing Aerogels via Synergistic Effects of Electrostatic In-Plane and Dispersive π-π-Stacking Interactions

A new strategy for CO₂ capture is reported based on the synergistic effect of electrostatic in-plane and dispersive π-π-stacking interactions of amide and indole with CO₂. Density functional theory illustrated that the amide group can have an increased ability to capture CO₂ molecules that were just desorbed from an adjacent indole unit. We used this strategy to fabricate a microporous aerogel that exhibited a superior CO₂ capture performance in both dry and wet conditions. The proposed synergistic effect is expected to be a new rationale for the design of CO₂ capture materials.

CFA-7: an interpenetrated metal–organic framework of the MFU-4 family

Structural characterization of a novel interpenetrated bistriazolate-based MOF followed by postsynthetic replacement of Zn²⁺ by M²⁺ ions (M = Co, Ni, Cu) represents a versatile approach towards redox-active MOFs.