A nitrogen-rich mesoporous polymer for photocatalytic hydrogen evolution from water

A Cobalt-Modified Covalent Triazine-Based Framework as an Efficient Cocatalyst for Visible-Light-Driven Photocatalytic CO2 Reduction

Photocatalytic CO₂ reduction into carbonaceous feedstock chemicals is a promising renewable energy technology to convert solar energy and greenhouse gases into chemical fuels. Here, a covalent triazine-based framework (CTF) is demonstrated as an efficient cocatalyst to reduce CO₂ under visible-light irradiation. The nitrogen-rich triazine moieties in CTF contribute to CO₂ adsorption, while the periodical pore structure of CTF favors the accommodation of CO₂ and electron mediator. Immobilization of cobalt species onto CTF promotes the photocatalytic activity with a 44-fold enhancement over pristine CTF and the optimal CO production rate of the obtained Co/CTFs was up to 50 μmol g^-1 h^-1 . The results of solid-state UV-vis diffuse reflectance spectra (UV-vis DRS), CO₂ adsorption and electrochemical impedance spectroscopy (EIS) illustrated that the increased activity was ascribed to the enhanced CO₂ capture capacity, improved absorption of visible-light and facilitated the transfer of charge from CTF to CO₂ molecules. The CTF not only serves as a substrate for active Co species, but also bridges the photosensitizer with cobalt catalytic sites for the efficient transfer of photoexcited electrons. This work highlights the capability and ease of fabricating covalent organic framework-based photocatalytic systems that are potentially useful for energy-conversion applications.

Recent progress in covalent organic framework thin films: fabrications, applications and perspectives

As a newly emerging class of porous materials, covalent organic frameworks (COFs) have attracted much attention due to their intriguing structural merits (e.g., total organic backbone, tunable porosity and predictable structure). However, the insoluble and unprocessable features of bulk COF powder limit their applications. To overcome these limitations, considerable efforts have been devoted to exploring the fabrication of COF thin films with controllable architectures, which open the door for their novel applications. In this critical review, we aim to provide the recent advances in the fabrication of COF thin films not only supported on substrates but also as free-standing nanosheets via both bottom-up and top-down strategies. The bottom-up strategy involves solvothermal synthesis, interfacial polymerization, room temperature vapor-assisted conversion, and synthesis under continuous flow conditions; whereas, the top-down strategy involves solvent-assisted exfoliation, self-exfoliation, mechanical delamination, and chemical exfoliation. In addition, the applications of COF thin films including energy storage, semiconductor devices, membrane-separation, sensors, and drug delivery are summarized. Finally, to accelerate further research, a personal perspective covering their synthetic strategies, mechanisms and applications is presented.

Porous Organic Polymers: An Emerged Platform for Photocatalytic Water Splitting

Porous organic polymers (POPs), known for its high surface area and abundant porosity, can be easily designed and constructed at the molecular level. The POPs offer confined molecular spaces for the interplay of photons, excitons, electrons and holes, therefore featuring great potential in catalysis. In this review, a brief summary on the recent development of some current state-of-the-art POPs for photocatalytic water splitting and their design principles and synthetic strategies as well as relationship between structure and photocatalytic hydrogen or oxygen evolution performance are presented. Future prospects including research directions are also proposed, which may provide insights for developing POPs for photocatalytic water splitting with our expectations.

Porous Organic Polymers: An Emerged Platform for Photocatalytic Water Splitting

Porous organic polymers (POPs), known for its high surface area and abundant porosity, can be easily designed and constructed at the molecular level. The POPs offer confined molecular spaces for the interplay of photons, excitons, electrons and holes, therefore featuring great potential in catalysis. In this review, a brief summary on the recent development of some current state-of-the-art POPs for photocatalytic water splitting and their design principles and synthetic strategies as well as relationship between structure and photocatalytic hydrogen or oxygen evolution performance are presented. Future prospects including research directions are also proposed, which may provide insights for developing POPs for photocatalytic water splitting with our expectations.

Novel Melamine/o-Phthalaldehyde Covalent Organic Frameworks Nanosheets: Enhancement Flame Retardant and Mechanical Performances of Thermoplastic Polyurethanes

Covalent organic frameworks (COFs) nanosheets prepared from condensation reaction between melamine and o-phthalaldehyde are first prepared through ball milling and then incorporated into thermoplastic polyurethanes (TPU) by solution mixing. Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectrometer are applied to characterize COFs nanosheets. It is observed apparently from TEM image that COFs nanosheets are obtained. Successful preparation of COFs nanosheets is proved further by vanishment of typical diffraction peak of COFs at around 23.5° in COFs nanosheets XRD pattern, appearance of quadrant and semicircle stretching of the s-triazine ring at 1568 and 1469 cm^-1 in FTIR spectra and N═C bond at 389.5 eV in N_1s high-resolution XPS spectra of COFs nanosheets. The thermal property, combustion behavior and mechanical performance of TPU naoncomposites are also investigated. Incorporation of COFs nanosheets into TPU contributes to char forming of TPU under nitrogen atmosphere and 14.3% decrease of peak heat release rate of TPU. Besides, the elongation at break, Young's modulus, and fracture strength of TPU nanocomposites increase sharply compared with that of neat one.