Explosive decomposition of a melamine-cyanuric acid supramolecular assembly for fabricating defect-rich nitrogen-doped carbon nanotubes with significantly promoted catalysis.

A facile and scalable approach for fabricating structural defect-rich nitrogen-doped carbon nanotubes (MCSA-CNTs) through explosive decomposition of melamine-cyanuric acid supramolecular assembly is presented. In comparison to pristine carbon nanotubes, MCSA-CNT exhibits significantly enhanced catalytic performance in oxidant- and steam-free direct dehydrogenation of ethylbenzene, demonstrating the potential for metal-free clean and energy-saving styrene production. This finding also opens a new horizon for preparing highly-efficient carbocatalysts rich in structural defect sites for diverse transformations.

Nitrogen-doped carbon nanotubes via a facile two-step approach as an efficient catalyst for the direct dehydrogenation of ethylbenzene.

A novel and efficient nitrogen-doped carbon nanotube (A-M-CNT) catalyst has been prepared by a facile two-step method, including prior air activation and subsequent pyrolysis of the carbon nanotubes with melamine. The as-synthesized A-M-CNT affords superior catalytic activity to the nitrogen-doped CNT without air activation (M-CNT) and pristine CNT, ascribed to its unique microstructure and surface chemical properties.

Plastering Sponge with Nanocarbon-Containing Slurry to Construct Mechanically Robust Macroporous Monolithic Catalysts for Direct Dehydrogenation of Ethylbenzene.

Nanocarbons have shown great potential as a sustainable alternative to metal catalysts, but their powder form limits their industrial applications. The preparation of nanocarbon-based monolithic catalysts is a practical approach for overcoming the resulting pressure drop associated with their powder form. In our previous work, a ploycation-mediated approach was used to successfully prepare nanocarbon-containing monoliths. Unfortunately, because there are no macropores in the monolith, it needs to be crashed into millimeter-sized particles before application. Therefore, developing a facile method for preparing mechanically robust nanocarbon-based macroporous monolithic catalysts is vital but still challenging. Herein, evoked by swallows building their nests, we report an approach for successfully preparing a mechanically robust nanodiamond-based macroporous monolith catalyst by plastering melamine sponge (MS) with a slurry composed of nanodiamonds (NDs) and poly(imidazolium-methylene) chloride (PImM) followed by an annealing process. The macroporous monolith catalyst (ND/NCMS-NCPImM) containing NDs well dispersed in N-doped carbon is mechanically robust with enriched macroscopic pores. It exhibits outstanding catalysis toward ethylbenzene to styrene through a direct dehydrogenation reaction with a high styrene rate in a steady state (5.50 mmol g-1 h-1) and high styrene selectivity (99.5%). ND/NCMS-NCPImM shows much higher activity than powder ND by 1.9 fold. In addition, this work solves the significant problem of large pressure drop encountered with conventional powdered nanocarbon catalysts in the flow reactor. This work not only creates an excellent nanodiamond-based macroporous monolithic ethylbenzene direct dehydrogenation catalyst but also presents a promising avenue for preparing other macroporous monolithic catalysts for diverse transformations.

Reconstructing Supramolecular Aggregates to Nitrogen-Deficient g-C3N4 Bunchy Tubes with Enhanced Photocatalysis for H2 Production.

Developing a facile method to overcome the intrinsic shortcomings of g-C3N4 photocatalyst concerning its insufficient visible light absorption and dissatisfactory separation efficiency of charge carriers is of great significance but remains a challenge. In this work, we report, for the first time, a sapiential strategy for preparing highly efficient nitrogen-deficient g-C3N4 featuring bunchy microtubes [R-tubular carbon nitride (TCN)] via a KOH-assisted hydrothermal treatment of rodlike melamine-cyanuric acid (RMCA) supramolecular aggregates followed by heating the reconstructed RMCA, in which KOH serves as an all-rounder for breaking hydrogen bonds, accelerating hydrolysis of melamine and nitrogen defects forming. This approach endows R-TCN with unique bunchy microtube morphology, enriched nitrogen defects, textural properties, and electronic structure, which result in narrower band gap, higher electric conductivity, more active sites, more negative conductive band, significantly increased visible light harvesting capability, and improved separation efficiency of charge carriers. As a consequence, R-TCN shows 2.44 and 39 times higher hydrogen evolution rate (8.19 µmol h-1) than that of the pristine TCN from RMCA and bulk g-C3N4 from melamine. This new discovery may open a new avenue to fabricate highly efficient g-C3N4 catalysts.