Rational design of metal node-modified Ti-based MOFs for selective photoreduction of carbon dioxide to ethanol by computational screening

Abstract

In this work, density functional theory (DFT) calculations were conducted to investigate a series of metal node-modified Ti-MOF catalysts using transition metals (Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Os, Ir, and Au) introduced into Ti-ATA (ATA = 2-aminoterephthalic acid) for the photocatalytic reduction of CO₂ to C₂ products. CO₂ can be sufficiently activated on Ti(M)-ATA but the adsorption configuration depends on the nature of M. Over Ti(Nb)-ATA, Ti(Ta)-ATA, Ti(Zr)-ATA and Ti(Hf)-ATA, the two *CHO species undergo C–C coupling to form *CHOCHO, an important C₂ intermediate. Ti(Nb)-ATA and Ti(Ta)-ATA tend to generate ethanol, while Ti(Zr)-ATA and Ti(Hf)-ATA are more selective to ethylene. Among the Ti(M)-ATA candidates studied, Ti(Nb)-ATA was identified as the most active catalyst for CO₂ reduction to ethanol due to its smallest limiting free energy change (1.12 eV), over which the *CH₂CH₂O reduction to *CH₂CH₂OH was found to be the rate-determining step. The correlation curve analysis illustrates that the reduction activity of Ti(M)-ATA catalysts is highly dependent on the binding strength of CO₂ and key reaction intermediates such as *OCHOH. The analysis of electronic and optical properties indicates that the altered energy band structure and charge transfer behavior around the bimetallic nodes of Ti(Nb)-ATA account for its excellent catalytic activity for CO₂ reduction to ethanol.