[Paper Review] Mechanism-driven CO2 Capture and Activation on Two-dimensional Transition-metal Diborides

Jakkapat Seeyangnok, Rungkiat Nganglumpoon+2 more|arXiv (Cornell University)|Feb 13, 2026

Boron and Carbon Nanomaterials Research0 citations

TL;DR

The paper uses first-principles DFT to show strong chemisorption and CO2 activation on hexagonal M2B2 monolayers (M=Sc,Y,Ti,Zr,Nb), driven by charge transfer from the surface to CO2, with Ti2B2 and Sc2B2 showing the strongest binding and potential for dissociation pathways.

ABSTRACT

The urgent need to mitigate rising atmospheric CO2 levels motivates the search for stable, efficient, and tunable adsorbent materials. In this study, we employ first-principles density functional theory to investigate the adsorption of CO2 molecules on two-dimensional hexagonal transition-metal diboride monolayers, M2B2 (M = Sc, Y, Ti, Zr, Nb). The adsorption energies, structural distortions, and bonding characteristics are systematically analyzed to understand how the metal center governs CO2 activation. The calculated adsorption energies range from -1.84 to -2.16 eV (or -1.98 to -4.42 eV), with Ti2B2 and Sc2B2 exhibiting the strongest CO2 binding, while Y2B2, Zr2B2, and Nb2B2 show moderately strong chemisorption. Adsorption induces significant molecular activation, evidenced by elongated C-O bonds (1.27-1.29 Angstrom) and bent O-C-O angles (129-132 degrees), compared to the linear gas-phase configuration (1.17 Angstrom, 180 degrees). Charge analysis further reveals substantial electron transfer from the monolayer to CO2, consistent with strong chemisorption and structural deformation. Correspondingly, the shift toward less negative IpCOHP(Ef) values indicates a pronounced weakening of the internal C-O bonds, reflecting increased population of antibonding pi* orbitals. Ab initio molecular dynamics simulations show that the activated CO2 species is thermally sensitive: while most M2B2 surfaces retain stable adsorption at 300 K, Ti2B2 drives spontaneous CO2 dissociation into CO and O, revealing a temperature-assisted activation pathway. These findings highlight how the choice of transition metal tunes electronic interactions, adsorption energetics, and activation pathways on M2B2 surfaces. Overall, this work identifies two-dimensional transition-metal diborides as promising candidates for next-generation CO2 capture and activation technologies.

Motivation & Objective

• Assess the structural stability of hexagonal M2B2 monolayers (M = Sc, Y, Ti, Zr, Nb) for potential CO2 applications.
• Evaluate CO2 adsorption energetics and binding configurations on M2B2 surfaces.
• Elucidate electronic structure changes and charge-transfer mechanisms during CO2 adsorption.
• Determine molecular activation indicators such as bond elongation, bending, and COHP changes.
• Explore thermal effects on adsorbed CO2 via ab initio molecular dynamics.

Proposed method

• Perform DFT calculations with PBE-GGA and PAW pseudopotentials using Quantum Espresso.
• Apply Grimme D3 corrections to capture dispersion interactions.
• Model CO2 adsorption on a 3x3x1 M2B2 surface supercell and calculate adsorption energies.
• Use Löwdin and Bader charge analyses to quantify charge transfer.
• Conduct COHP analysis with LOBSTER to assess C–O bond strength changes.
• Run ab initio molecular dynamics at 300 K to assess thermal stability and potential dissociation pathways.

Figure 1: Top (left) and side (right) views of the optimized atomic structure of two-dimensional hexagonal $\mathrm{M_{2}B_{2}}$ ( $\mathrm{M=Sc,Y,Ti,Zr,Nb}$ ) monolayer. The purple and green spheres represent the metal (M) and boron (B) atoms, respectively. The black lines indicate the primitive un

Experimental results

Research questions

• RQ1 What are the most favorable CO2 adsorption configurations on each M2B2 (M=Sc,Y,Ti,Zr,Nb) monolayer?
• RQ2 How does charge transfer from the M2B2 surface to CO2 influence C–O bond activation and antibonding orbital occupation?
• RQ3 Which M2B2 compositions lead to strongest adsorption and potential CO2 dissociation under thermal conditions?
• RQ4 How do vibrational and dynamical stability characteristics correlate with CO2 activation across the series?

Key findings

• Adsorption energies range from -1.84 to -2.16 eV, with Ti2B2 and Sc2B2 binding CO2 most strongly.
• CO2 bends (129–132°) and C–O bonds elongate to 1.27–1.29 Å upon adsorption, indicating activation.
• Löwdin and Bader analyses show significant electron transfer to CO2, forming CO2δ−; Nb donates least while Sc and Ti donate more.
• COHP analysis shows IpCOHP(Ef) shifts from -18.29 eV in isolated CO2 to -13.91 to -14.43 eV upon adsorption, reflecting weakened C–O bonds.
• AIMD at 300 K reveals surface-bound CO2δ− is thermally sensitive; Ti2B2 can spontaneously dissociate CO2 into CO and O, while Nb2B2 remains mostly stable.
• All pristine M2B2 monolayers are dynamically stable with no imaginary phonon modes.

Figure 2: Phonon dispersion relations of the pristine two-dimensional $\mathrm{M_{2}B_{2}}$ ( $\mathrm{M=Sc,Y,Ti,Zr,Nb}$ ) monolayers along the high-symmetry path $\Gamma$ –K–M– $\Gamma$ in the Brillouin zone. Panels (a)–(e) correspond to $\mathrm{Sc_{2}B_{2}}$ , $\mathrm{Y_{2}B_{2}}$ , $\mathrm{Ti_