Fluorescent Carbon Nitride Macrostructures Derived from Triazine‐Based Cocrystals

Abstract

Graphitic carbon nitrides (CNs) have attracted widespread attention during the last decade, thanks to their potential to address current materials science chal lenges, such as the production of solar fuels by photoelectrochemical means or the catalytic removal of organic pollu tants from water. [1][2][3][4][5] The possibility of tai loring parameters such as charge transfer kinetics, porosity, or energy band positions through approaches including doping, [6] templating, [7] covalent functionalization, [8,9] or the formation of heterojunctions [10] has opened the gate toward the application of CNbased materials in various fields, including bioimaging and electrochemi luminescent devices. [11][12][13][14] However, the rational design of CN materials for these applications remains in its infancy. Typically, to obtain CNbased highly emissive materials, topdown strategies or hydrothermal means are used [15,16] but they do not allow their scalability for industrial applications. Consequently, compatible synthesis with largescale production of CN powders suitable for solidstate fluorescentsensing platforms remains a challenge.During the last few years, our group and others have shown that the utilization of selfassembled supramolecular struc tures for the hightemperature synthesis of CN allows for the preservation of chemical bonds, morphologies, and electronic structures, which permits controlling of CN properties at the molecular level and their largescale production. [17] Notably, highly ordered supramolecular single crystals have been shown to be particularly useful in this regard. [18][19][20] In this work, we exploited these findings to synthesize new triazine based cocrystals composed of melamine and acetoguanamine (AGA), which were subsequently used as precursors for CN via hightemperature reaction. We tuned the precursor crystalline structures to endow the final CNs with a good photolumines cent behavior in both liquid and solid states, as demonstrated by their performance in detecting metal ions (in an aqueous environment) and labeling latent fingerprints (as a solidstate sensing platform). Results and DiscussionMelaminebased cocrystals were prepared by dissolving mela mine with different amounts of AGA in an aqueous solution Carbon nitride (CN) based materials have emerged as efficient photo-and electrocatalysts for various reactions. However, despite their intriguing optical properties (i.e., fluorescence), their utilization as solid-state sensing platforms remains in its infancy, owing to the formation of defect states during the materials synthesis, leading to low emission for the CN powder. Here, a bottom-up synthesis of CN macrostructures with good photoluminescence properties in both liquid and solid state is introduced, from designed triazinebased cocrystals with ordered morphology and tailored chemical composition. Upon calcination at 500 °C, the starting morphology and chemical composition are retained, resulting in the alteration of the HOMO-LUMO distribution of the CN materials, as further supporte...

Efficient Water Cleaning by Self‐standing Carbon Nitride Films Derived from Supramolecular Hydrogels

“…In order to study this synthetic approach with a wider variety of precursors, thereby showing its applicability to the synthesis of different materials, we replaced melamine with other precursors commonly employed in the preparation of photoactive polymers, namely urea, [48] dicyandiamide (DCD), [49] acetoguanamine (AGA), [50,51] and 2,4,6‐triaminopyrimidine (TAP), [52,53] and we studied the supramolecular self‐assembly behaviour of the resulting mixture. Amongst those monomers, we observed that only TAP was able to form a bulk hydrogel with cyanobenzoic acid, probably owing to the very similar structure and hydrogen‐bonding ability of TAP and MA [46,54] .…”

Carbon-Phosphorus-Nitrogen Materials as Highly Thermally Stable Catalyst Supports for CO2 Hydrogenation to Methanol

“…This observation agrees with previous reports, which demonstrate the merit of using supramolecular crystalline materials as precursors to control the structure of the final materials. 22,24,25 The XRD patterns of the CPN x display signals corresponding to an amorphous structure, with a single broad diffraction peak located at 23.1°(Figure S1a). FTIR spectra confirmed the formation of a polyphosphazene network: the C−O−P stretching vibration is visible at 750 cm −1 , and the stretching modes of phosphate groups, ν(P−O−P) 26 and ν(P�O), 27 and heptazine units, ν(C−N/C−N�C), 28 can be seen at 915, 1222, and 2162 cm −1 , respectively (Figure S1b).…”

g-C3N4: Properties, Pore Modifications, and Photocatalytic Applications

“…By using such supramolecular single crystals as a precursor, the obtained needle-like porous CN nanostructure had an SSA of 185 m 2 ·g −1 , and an increased visible light absorption capacity in range of 450–600 nm. Besides, triazine-based cocrystals composed of two types of molecular units by non-covalent interactions, such as acetoguana-mine-melamine [ 158 ] and terephthalic acid-melamine [ 159 ], were selected as precursors for porous CN via pyrolysis. MOFs have emerged as a new type of precursors for porous carbons-based material and metal/carbon composites [ 160 , 161 ].…”