Infrared Spectroscopic Study of the Adsorption Forms of Cyanuric Acid and Cyanuric Chloride on TiO₂

Abstract

Cyanuric acid is often found to be the end product in the hydrolysis of waste melamine and in the TiO2-mediated photocatalytic decomposition of s-triazine-containing compounds used as herbicides or dyes. The photocatalytically recalcitrant nature of cyanuric acid on TiO2 may be closely related to its adsorption properties, including the tautomeric forms present on the surfaces and their bonding structures, which remain to be determined. In this paper, we present the optimized adsorption structures of the four tautomeric isomers (triketo, diketo, monoketo, and triol) of cyanuric acid on a model rutile-TiO2(110) surface and their vibrational absorptions. Experimentally, the adsorption structures of cyanuric acid and chloride on powdered TiO2 are analyzed on the basis of the theoretically obtained, characteristic infrared information. Cyanuric acid on TiO2 at 35 °C exists in triketo and hydroxylated forms, but the diketo becomes the predominant form on the surface at 250 °C, being bonded to a titanium site via one of its carbonyl groups and with a N-H···O hydrogen bonding interaction. Hydroxylation of cyanuric chloride occurs as it is adsorbed on TiO2 at 35 °C. Upon being heated to 200 °C, the surface is mainly covered with the diketo form of cyanuric acid after the adsorption of cyanuric chloride.

Improved Quantum Yield and Excellent Luminescence Stability of Europium‐Incorporated Polymeric Hydrogen‐Bonded Heptazine Frameworks Due to an Efficient Hydrogen‐Bonding Effect

“…The v (N‐H) stretching peaks at 3490 and 3427 cm −1 and the CN and CN stretching peaks at 1605 and 1252 cm −1 were found to become progressively weaker for the P‐HHF‐Eu samples. [ 22 ] Another change is the development of a peak at 2180 cm −1 , corresponding to an asymmetric stretching vibration of cyanamide groups (H 2 NCN). [ 23 ] These results further confirm that increasing the Eu 3+ concentration during the synthesis of P‐HHF‐Eu introduces CN groups and consumes the NHx groups, which might originate from the breakage of the heptazine nucleus and the formation of N–Eu bonds.…”

“…[ 23 ] These results further confirm that increasing the Eu 3+ concentration during the synthesis of P‐HHF‐Eu introduces CN groups and consumes the NHx groups, which might originate from the breakage of the heptazine nucleus and the formation of N–Eu bonds. [ 22b,23,24 ] The morphologies of the P‐HHF and P‐HHF‐Eu samples were investigated by scanning and transmission electron microscopy (SEM and TEM). As shown in Figure S3, Supporting Information, the pristine P‐HHF as well as the P‐HHF‐Eu samples have a similar but quite irregular morphology consisting of small flakes and large agglomerates with a particle size between 0.2 and 2 µm.…”

Dual-Photoelectrode Fuel Cell Based Self-Powered Sensor for a Picomole Level Pollutant: Using an In Situ Molecularly Imprinted p-Type Organic Photocathode

“…As shown in Figure F, the infrared signal peak at 1260 cm –1 belongs to the in-plane bending vibration peak of O–H, showing that there are a large number of hydroxyl groups on the surface of pTTh. The signal of MI-pTTh is significantly higher than that of NI-pTTh, implying the molecular imprinting functionalization changes the micromorphology and interface properties of pTTh, making it contain more hydroxyl groups, which is conducive to providing more active sites for the formation of hydrogen bonds with the target molecules ATZ. , As shown in Figure G, after incubation with ATZ, MI-pTTh shows the in-plane deformation peak of the triazine ring in 1543 cm –1 and the stretching vibration peak of CN in 1625 cm –1 . While the stretching vibration peak of CC (1660 cm –1 ) and the skeleton vibration peak of the thiophene ring (1590 cm –1 ) decrease significantly, which is attributed to the interaction between the π-orbital of the triazine ring and the π-orbital of the thiophene ring .…”

Structure-Based Design and Synthesis of a New Phenylboronic-Modified Affinity Medium for Metalloprotease Purification

“…To find the optimal spacer arm, two different lengths of linear arms (5-atom spacer and 10-atom spacer) and a cyclic arm (cyanuric chloride) were tested. Cyanuric chloride is a typical cyclic compound containing the s -triazine (C 3 N 3 ) ring that could supply a higher mechanical strength for the ligand stabilization and was widely used in the affinity medium synthesis [ 38 , 39 , 40 , 41 ]. The scheme for the synthesis of media with the 5-atom spacer and the 10-atom spacer are shown in Figure 2 C,D, correspondingly.…”