Ammonia is an indispensable commodity in the agricultural and pharmaceutical industries. Direct nitrate‐to‐ammonia electroreduction is a decentralized route yet challenged by competing side reactions. Most catalysts are metal‐based, and metal‐free catalysts with high nitrate‐to‐ammonia conversion activity are rarely reported. Herein, it is shown that amorphous graphene synthesized by laser induction and comprising strained and disordered pentagons, hexagons, and heptagons can electrocatalyze the eight‐electron reduction of NO3− to NH3 with a Faradaic efficiency of ≈100% and an ammonia production rate of 2859 µg cm−2 h−1 at −0.93 V versus reversible hydrogen electrode. X‐ray pair‐distribution function analysis and electron microscopy reveal the unique molecular features of amorphous graphene that facilitate NO3− reduction. In situ Fourier transform infrared spectroscopy and theoretical calculations establish the critical role of these features in stabilizing the reaction intermediates via structural relaxation. The enhanced catalytic activity enables the implementation of flow electrolysis for the on‐demand synthesis and release of ammonia with >70% selectivity, resulting in significantly increased yields and survival rates when applied to plant cultivation. The results of this study show significant promise for remediating nitrate‐polluted water and completing the NOx cycle.

Developing metal-free electrocatalysts for direct nitrate-to-ammonia reduction is promising to remediate wastewater yet challenged by the poor ammonia selectivity. Amorphization has become an emerging strategy to afford conventional materials with exotic physical, chemical, and electronic properties. Transient laser heating of polymers produces graphene with an unusual polycrystalline lattice, yet the control of graphene amorphicity is difficult due to the extreme conditions and fast kinetics of the lasing process. Here, we report the synthesis of amorphous graphene with a tailorable heterophase, topologically disparate from crystalline graphene and amorphous carbon. Atomic-resolution imaging reveals the intermediate crystallinity comprising both six-membered rings and polygons, the ratio of which directly correlates with the aromatic structures of the precursors. These amorphous graphenes, as metal-free catalysts, show high performance in direct nitrate-to-ammonia electroreduction. The performance is associated with the amorphicity of graphene and reaches a maximum ammonia Faradaic efficiency of 83.7% at −0.94 V vs reversible hydrogen electrode. X-ray pair distribution functions and paramagnetism disclose the elongated carbon–carbon bonds and rich unpaired electrons in amorphous graphene, which exhibit more favorable adsorption of nitrate as suggested by theoretical calculations. Our findings shed light on the controllable synthesis of graphene with unusual topologies that could find broad applications in electronics, catalysis, and sensors.

A series of tetracoordinate boron-doped polycyclic aromatic hydrocarbons have been synthesized under mild conditions, featuring delayed fluorescence and aggregation-induced emission.

The incorporation of heteroatoms and/or heptagons as the defects into helicenes expands the variety of chiroptical materials with novel properties. However, it is still challenging to construct novel boron‐doped heptagon‐containing helicenes with high photoluminescence quantum yields (PLQYs) and narrow full‐width‐at‐half‐maximum (FWHM) values. We report an efficient and scalable synthesis of a quadruple helicene 4Cz‐NBN with two nitrogen‐boron‐nitrogen (NBN) units and a double helicene 4Cz‐NBN‐P1 bearing two NBN‐doped heptagons, the latter could be formed via a two‐fold Scholl reaction of the former. The helicenes 4Cz‐NBN and 4Cz‐NBN‐P1 exhibit excellent PLQYs up to 99 % and 65 % with narrow FWHM of 24 nm and 22 nm, respectively. The emission wavelengths are tunable via stepwise titration experiments of 4Cz‐NBN‐P1 toward fluoride, enabling distinguished circularly polarized luminescence (CPL) from green, orange (4Cz‐NBN‐P1‐F1) to yellow (trans/cis‐4Cz‐NBN‐P1‐F2) with near‐unity PLQYs and broader circular dichroism (CD) ranges. The five structures of the aforementioned four helicenes were confirmed by single crystal X‐ray diffraction analysis. This work provides a novel design strategy for construction of non‐benzenoid multiple helicenes exhibiting narrow emissions with superior PLQYs.

Modification of π-conjugated systems using a boron atom as the dopant has become a powerful approach to create new structures and new properties. Herein, we report a facile synthesis of replacing the carbon edges of [4]triangulene by three oxygen-boron-oxygen (OBO) units. The triangulenes are structurally similar to [4]triangulene and isoelectronic to the trianion of [4]triangulene. The structure of triangulene is confirmed by single-crystal X-ray diffraction analysis, revealing an off-plane core with three edgemodified OBO units. These triangulenes exhibit excellent thermal stability. These compounds have phosphorescence with lifetime longer than 1 s at 77 K. Both theoretical calculations and photophysical investigation of triangulenes indicate that this kind of molecules display a rare anti-Kasha fluorescence and phosphorescence emissions from multiple higher excited states.

The incorporation of heteroatoms and/or heptagons as the defects into helicenes expands the variety of chiroptical materials with novel properties. However, it is still challenging to construct novel boron‐doped heptagon‐containing helicenes with high photoluminescence quantum yields (PLQYs) and narrow full‐width‐at‐half‐maximum (FWHM) values. We report an efficient and scalable synthesis of a quadruple helicene 4Cz‐NBN with two nitrogen‐boron‐nitrogen (NBN) units and a double helicene 4Cz‐NBN‐P1 bearing two NBN‐doped heptagons, the latter could be formed via a two‐fold Scholl reaction of the former. The helicenes 4Cz‐NBN and 4Cz‐NBN‐P1 exhibit excellent PLQYs up to 99 % and 65 % with narrow FWHM of 24 nm and 22 nm, respectively. The emission wavelengths are tunable via stepwise titration experiments of 4Cz‐NBN‐P1 toward fluoride, enabling distinguished circularly polarized luminescence (CPL) from green, orange (4Cz‐NBN‐P1‐F1) to yellow (trans/cis‐4Cz‐NBN‐P1‐F2) with near‐unity PLQYs and broader circular dichroism (CD) ranges. The five structures of the aforementioned four helicenes were confirmed by single crystal X‐ray diffraction analysis. This work provides a novel design strategy for construction of non‐benzenoid multiple helicenes exhibiting narrow emissions with superior PLQYs.

The boron-doped polycyclic aromatic hydrocarbons (PAHs) have attracted ongoing attention in the field of optoelectronic materials due to their unique optical and redox properties. To investigate the effect of tetracoordinate boron in PAHs bearing N-heterocycles (indole and carbazole), a facile approach to four-coordinate boron-doped PAHs was developed, which does not require elevated temperature and pre-synthesized functionalized boron reactants. Five tetracoordinate boron-doped PAHs (NBNN-1 – NBNN-5) were synthesized with different functional groups. Two of them (NBNN-1 and NBNN-2) could further undergo oxidative coupling reactions to form fused off-plane tetracoordinate boron-doped PAHs NBNN-1f and NBNN-2f. Compared to the three-coordinate boron-doped counterparts, the UV/Vis absorption and fluorescent emission are significantly red-shift. Unlike the distinct impact of coordination number of boron on optoelectronic properties, the difference of functional groups on the boron atom has negligible impact on their optical and electrochemical properties. The compounds NBNN-1f and NBNN-2f show aggregation-induced emission.

Triangulenes have attracted enormous interest due to the intriguing properties. However, the limited synthetic approach and intrinsic instability make the investigation of their properties inaccessible. The synthesis of heteroatom-doped triangulenes becomes an alternative strategy of studying triangulenes. Herein, we report the synthesis of three [4]triangulenes, which are edge-modified by three oxygen-boron-oxygen (OBO) units. The structure of OBO-doped [4]triangulene is confirmed by the single-crystal X-ray diffraction analysis, revealing an off-plane core with three edge-modified OBO units. These OBO-doped [4]triangulenes exhibit high stability towards air and moisture. Both theoretical calculations and photophysical investigation of OBO-doped [4]triangulenes indicate that this kind of molecules display anti-Kasha fluorescence and phosphorescence emissions. The binding behaviors of (OBO)3-[4]triangulenes toward pyridine were also studied.