Isolated flat bands and physics of mixed dimensions in a 2D covalent organic framework

Synergistic effects of rare-earth ions (Ho, Yb) doping on the photo-catalytic efficacy of V2O5 for removal of pollutants from industrial waste water

The co-doping of vanadium pentoxide (V2O5) with rare-earth (RE) elements, namely 1.5 % holmium (Ho) and 1.5 % ytterbium (Yb) has been conducted using an eco-friendly, straightforward hydrothermal approach to assess the combined effects on structural, optical, and photocatalytic properties. The application of the density functional theory (DFT) approach effectively examined the impact of RE ions on the photocatalytic efficiency of co-doped V2O5. The stable orthorhombic crystal structure of co-doped V2O5 has been confirmed using DFT and X-ray diffraction without a secondary phase. It appears that homogeneous nucleation occurs while heterogeneous nucleation slows down in co-doped samples, as evidenced by the larger crystallite sizes in co-doped samples compared to doped ones. It means a result, the co-doped samples exhibit photodegrades more quickly and have a higher rate constant than the doped samples. This is because they have less dislocation density (4.26 × 10-3 nm-2) and internal micro-strain (4.93 × 10-3). The bandgap and degradation efficiency are determined by the UV-vis spectroscopy and found to be 2.33 eV and 95 %, respectively, at the optimal pH of 7 in the visible range. The co-doped sample has a rate constant of 24 × 10-3 min-1, which is the highest in the RE-doped V2O5 system. This is a good reason to think of co-doped V2O5 as a possible catalyst.

Quasiparticle electronic structure of two-dimensional heterotriangulene-based covalent organic frameworks adsorbed on Au(111)

The modular nature and unique electronic properties of two-dimensional (2D) covalent organic frameworks (COFs) make them an attractive option for applications in catalysis, optoelectronics, and spintronics. The fabrications of such devices often involve interfaces formed between COFs and substrates. In this work, we employ the first-principlesGWapproach to accurately determine the quasiparticle electronic structure of three 2D carbonyl bridged heterotriangulene-based COFs featuring honeycomb-kagome lattice, with their properties ranging from a semi-metal to a wide-gap semiconductor. Moreover, we study the adsorption of these COFs on Au(111) surface and characterize the quasiparticle electronic structure at the heterogeneous COF/Au(111) interfaces. To reduce the computational cost, we apply the recently developed dielectric embeddingGWapproach and show that our results agree with existing experimental measurement on the interfacial energy level alignment. Our calculations illustrate how the many-body dielectric screening at the interface modulates the energies and shapes of the Dirac bands, the effective masses of semiconducting COFs, as well as the Fermi velocity of the semi-metallic COF.