Toward Quantum Confinement in Graphitic Carbon Nitride-Based Polymeric Monolayers

Abstract

Graphitic carbon nitride (g-C3N4) has garnered much attention due to its potential as an efficient metal-free photocatalyst. This study examines the evolution of properties in zero-dimensional quantum dots up to sizable clusters that mimic extended g-C3N4 monolayers. We employ density functional theory to investigate systematically the structural, electronic, and optical properties of the g-C3N4-based melamine and heptazine building blocks using a “bottom-up” construction of polymeric monolayers. The results from our computations indicate that the melamine- and heptazine-based polymeric g-C3N4 systems must be reduced to at least 2.74 and 4.00 nm, respectively, to observe an increase of its optical gap with a size reduction. The present study also examines the nature of the electronic transitions exhibited by g-C3N4-based monolayers through full natural transition orbital and density of state analyses. The most promising sites for water splitting and subsequent chemical doping studies are identified, which generally correspond to the nitrogen and carbon atoms, respectively.

Tuning the electronic and optical properties of hg-C3N4 quantum dots with edge-functionalization: a computational perspective

“…The E g obtained for 1–Pris (4.67 eV) and 3–Pris (3.55 eV) QDs using HSE06 functional are relatively closer to the values reported in the literature. 40 The trends observed in the shifting of the HOMO and LUMO levels for the pristine and corresponding functionalized cases are similar to those of the B3LYP based results.…”

“…S2(a) of the ESI †], it is clear that the HOMO is localized on the nitrogen atoms, whereas the LUMO is delocalized and mainly distributed over the C-N bonds and located on the nitrogen atoms present at the boundary, in agreement with the literature. 40,44 After functionalization of 1-Pris QD, the type of spatial distribution of both the HOMO (localized) and LUMO (delocalized) remains unaffected. In addition to this, LUMO also gets distributed over the atoms of the attached functional groups except in the case of -CH 3 group.…”

“…38 Ghashghaee et al 39 compared the geometric structure and electronic properties of heptazine-based g-C 3 N 4 (hg-C 3 N 4 ) QDs and 2D g-C 3 N 4 . Olademehin et al 40 reported the electronic and optical properties of triangular shaped g-C 3 N 4 QDs of increasing sizes, designed using melamine (triazine) and heptazine units. Their study also demonstrated that the carbon and nitrogen sites would be more favorable for HER and OER, respectively.…”

Shedding Light on the Vibrational Signatures in Halogen‐Bonded Graphitic Carbon Nitride Building Blocks

“…[42,49] Graphitic carbon nitride building blocks, namely melamine and heptazine, are known for their highly desirable photocatalytic properties. [50][51][52][53] The interactive nitrogen atoms in the π-conjugated backbone of s-triazine provide the capacity to simultaneously host multiple NCIs. This is certainly true for halogen bonding, where the transfer of electron density from the XB acceptor (or electron donor) to the XB donor (or electron acceptor) is modulated by the electropositive σ-hole.…”

“…Graphitic carbon nitride building blocks, namely melamine and heptazine, are known for their highly desirable photocatalytic properties [50–53] . The interactive nitrogen atoms in the π ‐conjugated backbone of s ‐triazine provide the capacity to simultaneously host multiple NCIs.…”