In Situ Formation of Arrays of Tungsten Single Atoms within Carbon Nitride Frameworks Fabricated by One-Step Synthesis through Monomer Complexation
Barış Kumru, Daniel Cruz, Tobias Heil, Markus Antonietti
Abstract
Deposition of stable single atoms on supports is a hot topic, especially for catalysis, and single atom deposition in nitrogen-framed pores of carbon and carbon nitrides is indeed the most successful. The polymeric semiconductor graphitic carbon nitride (g-CN) is an exciting scaffold due to its nitrogen-rich structure (C3N4 ideally) and the inherent nitrogen-lined pores, which made the whole, structurally diverse g-CN family an attractive choice for heterogeneous catalysis and photocatalysis. Herein, we present the simple thermal treatment of a monomer complex between melamine and silicotungstic acid to yield massive amounts of tungsten single atoms within the carbon nitride framework. The morphology and photophysical properties of the novel semiconductor with a band gap around 2 eV are investigated in dependence of the tungsten content, and the onset of W–W exchange interactions will be described. Due to the ease of W to change the oxidation state and to bind to oxygen atoms, the material turns out to be an effective catalyst for oxidation reactions, which was exemplified with new oxidative photopolymerization of guaiacol to form artificial lignin-like polyphenols.