Regulating the spin state of single-atom doped covalent triazine frameworks for efficient nitrogen fixation

Understanding electron structure of covalent triazine framework embraced with gold nanoparticles for nitrogen reduction to ammonia

Regulating the electron structure and precise loading sites of metal-active sites within the highly conjugated and porous covalent-triazine frameworks (CTFs) is essential to promoting the nitrogen reduction reaction (NRR) performance for electrocatalytic ammonia (NH3) synthesis under ambient conditions. Herein, experimental method and density functional theory (DFT) calculations were conducted to deeply probe the effect on NRR of the modulation of modulating the electron structure and the loading site of gold nanoparticles (Au NPs) in a two-dimensional (2D) CTF. 2D CTF synthesized using melem and hexaketocyclohexane octahydrate as building blocks (denoted as M-HCO-CTF) served as a robust scaffold for loading Au NPs to form an M-HCO-CTF@AuNP hybrid. DFT results uncovered that well-defined Au sites with tunable local structure were the active site for driving the NRR, which can significantly suppress the conversion of H+ into *H adsorption and enhance the nitrogen (N2) adsorption/activation. The overlapped Au (3d) and *N2 (2p) orbitals lowered the free energy of the rate-determining step to form *NNH, thereby accelerating the NRR. The M-HCO-CTF@AuNPs electrocatalyst exhibited a large NH3 yield rate of 66.3 μg h-1 mg-1cat. and a high Faraday efficiency of 31.4 % at - 0.2 V versus reversible hydrogen electrode in 0.1 M HCl, superior to most reported CTF-based ones. This work can provide deep insights into the modulation of the electron structure of metal atoms within a porous organic framework for artificial NH3 synthesis through NRR.

Efficient integration of covalent triazine frameworks (CTFs) for augmented photocatalytic efficacy: A review of synthesis, strategies, and applications

Heterogeneous photocatalysis emerges as an exceptionally appealing technological avenue for the direct capture, conversion, and storage of renewable solar energy, facilitating the generation of sustainable and ecologically benign solar fuels and a spectrum of other pertinent applications. Heterogeneous nanocomposites, incorporating Covalent Triazine Frameworks (CTFs), exhibit a wide-ranging spectrum of light absorption, well-suited electronic band structures, rapid charge carrier mobility, ample resource availability, commendable chemical robustness, and straightforward synthetic routes. These attributes collectively position them as highly promising photocatalysts with applicability in diverse fields, including but not limited to the production of photocatalytic solar fuels and the decomposition of environmental contaminants. As the field of photocatalysis through the hybridization of CTFs undergoes rapid expansion, there is a pressing and substantive need for a systematic retrospective analysis and forward-looking evaluation to elucidate pathways for enhancing performance. This comprehensive review commences by directing attention to diverse synthetic methodologies for the creation of composite materials. And then it delves into a thorough exploration of strategies geared towards augmenting performance, encompassing the introduction of electron donor-acceptor (D-A) units, heteroatom doping, defect Engineering, architecture of Heterojunction and optimization of morphology. Following this, it systematically elucidates applications primarily centered around the efficient generation of photocatalytic hydrogen, reduction of carbon dioxide through photocatalysis, and the degradation of organic pollutants. Ultimately, the discourse turns towards unresolved challenges and the prospects for further advancement, offering valuable guidance for the potent harnessing of CTFs in high-efficiency photocatalytic processes.

Regulating the Flexibility to Assemble Porous Single-Atom Fe-Coordinated Metallopolymers for Efficient Heterogeneous Catalytic Oxidations

Metallopolymers as organic-inorganic hybrid materials formulated by metal embedding organic polymers show great potential for novel heterogeneous catalysis, in terms of the facile structural design and tunability. Herein, the disadvantage of nonporous stacking of one-dimensional (1D) structures has been suppressed by chain modulation of the 1D metallopolymers, allowing for the convenient construction of porous assemblies with single-atom dispersion and accessible active sites. By postmodification, the Fe/CM-1 catalyst readily synthesized by coordinating the Fe(II) to the twisted chain of 1D Schiff-base polymer possesses expedient flexibility, showing the highest porosity, remarkable heterogeneous recyclability, and thus prominent catalytic activity for the selective oxidation of benzylamine and alcohols. Moreover, control experiments supported by computational studies demonstrated that the unique pincer structure of Fe/CM-1 effectively maintains the valence state of the anchored single-atom iron, facilitating single-electron transfer and promoting efficient iron redox cycling during the catalytic process. Notably, these 1D metallopolymers have the advantage of cost-effectiveness, easy preparation in gram-scale, and utilization in continuous reaction, providing inspirations for facile synthesis of efficient heterogeneous catalysts from the well-developed 1D metallopolymers.