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Unraveling H2 dissociation in CO2 hydrogenation on frustrated Lewis pair-functionalized UiO–67: DFT and nuclear quantum effects
(2025-12-04)
Yodsin, Nuttapon
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Udagawa, Taro
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Daengngern, Rathawat
;
Jungsutthiwong, Siriporn
;
Tachikawa, Masanori
Understanding hydrogen (H<inf>2</inf>) activation is fundamental to developing efficient CO<inf>2</inf> hydrogenation catalysts. Thus, in this study, we examine H<inf>2</inf> dissociation and subsequent CO<inf>2</inf> hydrogenation on 12 UiO–67 frameworks functionalized with frustrated Lewis pairs (FLPs), employing both conventional density functional theory (DFT) and multicomponent DFT (MC_DFT) to account for nuclear quantum effects (NQEs). The results reveal that all FLP–MOFs lower the H<inf>2</inf> activation barrier through heterolytic cleavage, with NQEs further reducing the barriers—most notably in systems containing electron-donating groups (EDGs), where pronounced H–H bond elongation characterizes the transition state. Conversely, FLPs bearing strong electron-withdrawing groups stabilize the 2H adsorption state, rendering H<inf>2</inf> dissociation thermodynamically favorable but suppressing CO<inf>2</inf> hydrogenation owing to excessively strong hydrogen binding. Strong correlations are observed among H<inf>2</inf> dissociation energies, CO<inf>2</inf> hydrogenation activation barriers, and FLP acidity, enabling catalytic performance prediction. Incorporating NQEs enhances these correlations, providing a refined descriptor for rational catalyst screening. Overall, this study highlights the critical role of NQEs in hydrogen activation and demonstrates that EDG-functionalized FLP–MOFs are particularly promising candidates for promoting H<inf>2</inf> activation and CO<inf>2</inf> conversion.
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Unlocking efficient CO2–to–methanol conversion on frustrated Lewis pair-functionalized UiO–67: A synergistic approach using DFT and SISSO
(2025-10-01)
Yodsin, Nuttapon
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Pimbaotham, Pimjai
;
Maihom, Thana
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Daengngern, Rathawat
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Tachikawa, Masanori
Metal–organic framework-based catalysts demonstrate considerable promise for converting CO<inf>2</inf> into valuable chemicals, particularly when combined with Frustrated Lewis Pairs (FLPs) to enhance H<inf>2</inf> dissociation during hydrogenation reactions. This study employs density functional theory (DFT) calculations to investigate modified UiO–67 frameworks wherein FLPs are introduced via eight different functional groups (UiO–67–X) into the organic linker to facilitate H<inf>2</inf> activation during CO<inf>2</inf> hydrogenation to methanol (CH<inf>3</inf>OH). The reaction proceeds through three stages: (i) hydrogenation of CO<inf>2</inf> to formic acid (HCOOH), (ii) conversion of HCOOH to formaldehyde (HCHO), and (iii) hydrogenation of HCHO to CH<inf>3</inf>OH. This study specifically focuses on steps (ii) and (iii), analyzing the detailed reaction mechanisms using optimized molecular structures and Gibbs free energy calculations to acquire insights into methanol formation on UiO–67–X. During HCOOH conversion to HCHO, adsorbed H<inf>2</inf> undergoes heterolytic cleavage at the FLP sites, producing a proton (H+) and a hydride (H−) for subsequent HCOOH hydrogenation and dehydration. The energy barriers identified at this stage represent key kinetic limitations hindering efficient CO<inf>2</inf>-to-methanol conversion. Similarly, HCHO conversion to CH<inf>3</inf>OH proceeds via H<inf>2</inf> dissociation, followed by concerted H+/H− transfer. Among the tested UiO–67–X catalysts, UiO–67–B(CH<inf>3</inf>)<inf>2</inf> exhibits the highest catalytic activity for CO<inf>2</inf> hydrogenation to methanol. Kinetic analyses are performed to assess reaction rates across a relevant temperature range, highlighting the notable influence of functional groups on catalytic performance. Additionally, the Sure Independence Screening and Sparsifying Operator (SISSO) machine-learning approach is used to identify optimal physical descriptors and derive a predictive model for the energetic span (δG), considerably lowering the computational cost associated with full reaction pathway calculations. Statistical validation confirms the robustness of these predictions. Overall, these findings underscore the vital role of FLP-assisted H<inf>2</inf> dissociation in promoting CO<inf>2</inf> hydrogenation to CH<inf>3</inf>OH, with UiO–67–B(CH<inf>3</inf>)<inf>2</inf> serving as a promising catalyst.
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Nuclear quantum and H/D isotope effects on three-centered bonding diborane: Path integral molecular dynamics simulations
(2020-05-15)
Daengngern, Rathawat
;
Kobayashi, Osamu
;
Kungwan, Nawee
;
Ngaojampa, Chanisorn
;
Tachikawa, Masanori
Nuclear quantum and H/D isotope effects of bridging and terminal hydrogen atoms of diborane (B<inf>2</inf>H<inf>6</inf>) molecules were systematically studied by classical ab initio molecular dynamics (CLMD) and ab initio path integral molecular dynamics (PIMD) simulations with BHandHLYP/6-31++G** level of theory at room temperature (298.15 K). Calculated results clearly show that H/D isotope effect appears in the distribution of hydrogen (deuterium) of B<inf>2</inf>H<inf>6</inf> (B<inf>2</inf>D<inf>6</inf>). Geometry of B<inf>2</inf>H<inf>6</inf> also plays a significant role in the nuclear quantum effect proved by PIMD simulations, but slightly deviated from its equilibrium structure when simulated via CLMD simulation. The bond lengths between boron atoms R (B1 … B2) and the bridging hydrogen atoms R<inf>HH</inf> (H<inf>B</inf>1 … H<inf>B</inf>2) of the B<inf>2</inf>H<inf>6</inf> molecule obtained from PIMD simulations are slightly longer than those of the deuterated form of the diborane (B<inf>2</inf>D<inf>6</inf>) molecule. The principal component analysis (PCA) was also employed to distinguish the important modes of bridging hydrogen as related to the nuclear quantum and H/D isotope effects. The highest level of contribution obtained from PCA of PIMD simulations is bending, while various mixed vibrations with less contribution were also found. Therefore, the nuclear quantum and H/D isotope effects need to be taken into account for a better understanding of diborane geometry.

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