A highly proton conductive perfluorinated covalent triazine framework via low-temperature synthesis.

Proton-conducting materials are essential to the emerging hydrogen economy. Covalent triazine frameworks (CTFs) are promising proton-conducting materials at high temperatures but need more effective sites to strengthen interaction for proton carriers. However, their construction and design in a concise condition are still challenges. Herein, we show a low temperature approach to synthesize CTFs via a direct cyclotrimerization of aromatic aldehyde using ammonium iodide as facile nitrogen source. Among the CTFs, the perfluorinated CTF (CTF-TF) was successfully synthesized with much lower temperature ( ≤ 160 °C) and open-air atmosphere. Due to the additional hydrogen-bonding interaction between fluorine atoms and proton carriers (H3PO4), the CTF-TF achieves a proton conductivity of 1.82 × 10-1 S cm-1 at 150 °C after H3PO4 loading. Moreover, the CTF-TF can be readily integrated into mixed matrix membranes, displaying high proton conduction abilities and good mechanical strength. This work provides an alternative strategy for rational design of proton conducting media.

Rapid Synthesis of Covalent Organic Frameworks with a Controlled Morphology: An Emulsion Polymerization Approach via the Phase Transfer Catalysis Mechanism.

Covalent organic frameworks (COFs) with a periodic network of permanent porosity and ordered structures have witnessed enormous potential in many applications. However, the synthesis of COFs with controllable morphologies under mild conditions remains a critical issue. Herein, we report a novel strategy to synthesize ß-ketoenamine-linked COFs by emulsion polymerization via phase transfer catalysis for the first time. This new approach employs commercially available pyridinium surfactants as emulsifiers for emulsion polymerization, which function as both catalysts and morphological regulators. By controlling the interfacial interaction in the emulsion, the TpPa-COF can be prepared into different morphologies, i.e., spheres, bowls, and fibers. Furthermore, the COF emulsion can be directly used to prepare a film by applying an electric field, providing a new route to prepare COF films. This phase transfer catalysis method also allows the synthesis of the TpPa-COF on a gram scale. The strategy is fast, facile, and effective in improving the morphology and particle size, providing a prospective route for the green preparation of functional COFs.

Covalent Pyrimidine Frameworks via a Tandem Polycondensation Method for Photocatalytic Hydrogen Production and Proton Conduction.

The development of heteroaromatic conjugated porous polymers (H-CPPs) have received enormous research interests, because of the important functional roles of the heteroatoms in photocatalysis and proton conduction. However, due to the synthetic challenges deriving from the stable structures, the structural diversity and synthetic methods of them are still limited. Herein, a new type of H-CPPs, covalent pyrimidine frameworks (CPFs), via an efficient tandem polycondensation reaction between aldehyde, acetyl, and amidine monomers is reported. The resulting CPFs are bridged by pyrimidine units, rich of nitrogen atoms and can be structurally regulated on demand. The CPFs are shown to be active photocatalysts for hydrogen evolution from methanol via a photo-thermo-catalysis process, achieving an excellent hydrogen evolution rate of 5282.8 µmol h-1  g-1 . The CPFs can be further processed into a mixed matrix membrane, displaying an excellent proton conductivity of 1.30 × 10-2  S cm-1 at 413 K under anhydrous condition.

Covalent triazine frameworks constructed via benzyl halide monomers showing high photocatalytic activity in biomass reforming.

Here we report the synthesis of covalent triazine frameworks (CTFs) using benzyl halide monomers which are more cost-effective and with higher availability than previous ones. The resulting CTFs were successfully applied for efficient photocatalytic reforming of glucose for the first time, with a high hydrogen evolution rate up to 330 µmol g-1 h-1 under pH = 12. This work presented a new way to synthesize CTFs and further exhibited their potential applications in photocatalytic biomass reforming.