Interspersed Bi Promoting Hot Electron Transfer of Covalent Organic Frameworks Boosts Nitrogen Reduction to ammonia

Abstract

a large amount of pollution. [2] Therefore, the increasingly acute issues of the energy dilemma and environmental pollution have spurred intensive researches to develop environmental-friendly and renewable ways to produce NH 3 . In this context, photocatalytic nitrogen (N 2 ) fixation has been viewed as a suitable alternative for the traditional Haber-Bosch process.The unique properties of N 2 , including the extreme dissociation energy of N≡N (941 kJ mol −1 ), the high ionization potential, and the passive amount of electron affinity, resulting in the fact that the process of N 2 fixation to NH 3 rarely happens under moderate conditions. [3] Nevertheless, the triple bonds of N 2 still have an opportunity to be weakened and activated when electrons in the catalysts occupied the antibonding orbitals of nitrogen atoms or the depletion of N 2 occupied p-orbital electrons through σ-bond coordination. [4] Therefore, effective adsorption of N 2 and sufficient photogenerated electrons are exactly crucial to enhance the performance of NH 3 production. To date, various conventional photocatalysts (TiO 2 , KNbO 3 , or In 2 O 3 , for instance) have been thoroughly investigated for photocatalytic N 2 reduction reaction (NRR). [5][6][7] Most of them, however, are subjected to inferior efficiency because photogenerated electrons tend to recombine with holes, lack of competent active sites for adsorbing and activating N 2 , and low solar energy utilization rate. Especially, many of them have unsatisfactory activity toward NRR owing to their poor ability for water oxidation (2H 2 O + 4h + → O 2 + 4H + ) and need the presence of hole scavengers (ethanol or methanol) that could greatly hasten the evolution of NH 3 . [8] In addition, it's well known that the NRR process in liquid phase comprises multiphase-reactions and complicated transfer mechanisms, involving 6e − /6H + . By comparison, the HER process is much faster considering that only two electrons and two protons are involved, [9] finally contributing to the fact that plentiful active sites and photogenerated electrons are expended by the HER and then poor selectivity is exhibited. [10] From the above point of view, it is of grand significance to exploit efficient and stable photocatalysts for NRR.Covalent organic frameworks (COFs), a class of appearing crystalline photocatalysts with periodic framework structure, have attracted researchers' attention. The favorable Seeking highly-efficient, non-pollutant, and chemically robust photocatalysts for visible-light-driven ammonia production still remained challenging, especially in pure water. The key bottle-necks closely correlate to the nitrogen activation, water oxidization, and hydrogen evolution reaction (HER) processes. In this study, a novel Bi decorated imine-linked COF-TaTp (Bi/COF-TaTp) through N-Bi-O coordination is reasonably designed to achieve a boosting solar-to-ammonia conversion of 61 µmol −1 g −1 h −1 in the sacrificial-free system. On basis of serial characterizations and DFT calculations, the incorporated Bi ...

Covalent Organic Framework: An Emerging Catalyst for Renewable Ammonia Production

“…Considering COF's unique and tunable properties, plasmon‐enhanced COF could be the next‐generation photocatalyst for selective NRR. A recent report on interspersed Bi promoting hot electron transfer of COF increases the NRR [79] . Bi nanoparticles′ surface plasmon resonance (SPR) effect was responsible for the improved light absorption in this case.…”

“…A recent report on interspersed Bi promoting hot electron transfer of COF increases the NRR. [79] Bi nanoparticles' surface plasmon resonance (SPR) effect was responsible for the improved light absorption in this case.…”

“…These π‐conjugated electron‐rich COF structures are often anchored with i) a single atom (SAC), ii) bi atom (BAC), iii) a metalloid like boron, or iv) a highly conductive carbon nanotube (CNT) to achieve better yield and selectivity for renewable ammonia production via catalytic NRR. Table 1 briefly summarizes the details and compares the catalytic output of the recently developed COF‐based composites for catalytic NRR [25−30,32−34,60,76–81] . The composites with transition metal loading, whether SAC or BAC, exhibit exceptional theoretical faradic efficiency of up to 100 %.…”

Dual‐Plasmon Resonance Coupling Promoting Directional Photosynthesis of Nitrate from Air

“…With the increase of Bi loading capacity, the number and size of nanoparticles also increased. According to the high‐resolution TEM (HRTEM) image of Cs x WO 3 (Figure S3a,b) and Bi/Cs x WO 3 (Figure 1d–f), the characteristic interplanar distances of both Cs x WO 3 and Bi can be distinguished, with lattice distance of 0.322 nm and 0.380 nm corresponding to the (200) and (002) facet of hexagonal Cs x WO 3 [30] and lattice fringe of 0.328 nm and 0.227 nm corresponding to the (012) and (110) lattice plane of rhombohedral Bi [31] . Moreover, the energy dispersion spectrum (EDS) elemental mapping (Figure 1g–i) clearly shows the homogeneous distribution of Cs, W, O and Bi elements in the hybrid, which further verifies that Bi nanoparticles have been successfully grown on the surface of the Cs x WO 3 nanorods.…”

Efficient Hydrogen Peroxide Photosynthesis over CdS/COF for Water Disinfection: The S-Scheme Pathway, Oxygen Adsorption, and Reactor Design

“…Covalent organic frameworks (COFs) are a class of crystalline porous polymers that assemble various molecular building blocks into periodic arrays with tunable band gaps and energy band structure that can be precisely engineered, which can serve as ideal substrate for building heterojunctions. − These remarkable merits make COFs widely applicable in photocatalytic water purification, CO 2 reduction, , N 2 fixation, and organic matter conversion . Nevertheless, there have been relatively few reports on the photocatalytic production of H 2 O 2 using COFs.…”