Aqueous phase conversion of CO2 into acetic acid over thermally transformed MIL-88B catalyst
Summary¶
CO\(_2\) hydrogenation and C–C coupling in aqueous media are attractive routes to C\(_2\)+ chemicals, but efficient catalysts that operate in water with high selectivity to a single liquid product remain challenging. This Nature Communications article reports a thermally transformed MIL-88B catalyst in which Fe\(^0\) and iron-oxide motifs are embedded in a carbonaceous matrix, evaluated for aqueous-phase methanol hydrocarboxylation of CO\(_2\) toward acetic acid at 150 °C with LiI as a co-catalyst. The experimental program reports yield, selectivity, and recycling performance, while X-ray characterization supports a nanoscale picture of the active material after transformation. ReaxFF molecular simulations are used alongside experiments to propose plausible reaction pathways—including involvement of formic acid-class intermediates—in a way that connects atomistic bond-making and bond-breaking hypotheses to the observed macroscopic performance.
Methods¶
Catalyst synthesis and characterization¶
- Precursor: MIL-88B subjected to thermal transformation (temperature/atmosphere program in the article) yielding Fe\(^0\) / iron-oxide species embedded in a carbonaceous matrix.
- Characterization: X-ray and microscopy modalities listed in Nature Communications Methods track phase and Fe dispersion.
Catalytic experiments (aqueous CO₂ conversion)¶
- Conditions: Aqueous CO\(_2\) hydrocarboxylation with methanol and LiI co-catalyst at 150 °C (stirring, pressure, and stoichiometries per paper).
- Recycling: Up to five cycles reported in the abstract with yield/selectivity tracking.
ReaxFF molecular dynamics (B)¶
- Purpose: Explore plausible bond-making/breaking sequences consistent with acetic acid formation, including water-mediated chemistry and C–O rearrangements.
- Protocol: ReaxFF trajectories with cell, thermostat, and analysis choices documented in the computational section—not a substitute for measured kinetics.
MD application (integrated)¶
Engine / code: LAMMPS-class reactive MD with ReaxFF (as in the article). System & composition, slab vs cluster: Catalyst/aqueous/CO\(_2\)-related interfacial models; supercell sizes and stoichiometry in Nature Communications Methods and figures—N/A — not duplicated on this stub. PBC for bulk/solution cells unless the article specifies a cluster; N/A — frozen layers if not used. Ensemble: follow the article’s NVT or NPT stages; N/A here — thermostat/barostat types, damping, timestep (fs), and total trajectory length (ps/ns). Temperature: catalytic tests at 150 °C; MD setpoints (K) in the computational section. N/A — applied electric field; N/A — umbrella/metadynamics/REX. Pressure for autoclave/HP conditions: N/A in wiki copy—see full text.
Findings¶
Catalytic performance (abstract-reported)¶
High acetic acid yield on a per-catalyst mass basis with selectivity ~81.7% under the stated aqueous conditions (exact numbers in the article text/tables).
Catalyst structure¶
Characterization supports highly dispersed Fe\(^0\) and Fe(II)-oxide-related motifs in the transformed catalyst compared with the parent MOF.
Stability¶
Recycling shows no major loss of yield or selectivity over five cycles in the authors’ experiments.
Mechanistic modeling role¶
ReaxFF provides hypothesis-level support for pathways involving formic acid-class intermediates and related proton/C–O events—presented as qualitative insight, not fitted barriers or rates.
Limitations¶
ReaxFF provides qualitative mechanistic insight; absolute rates, barriers, and electrochemical effects in more complex electrolytes are not claimed to be fully captured by the force field. Operators should treat DFT or higher-level benchmarks as orthogonal validation if quantitative energetics are required.
Relevance to group¶
Demonstrates van Duin-group ReaxFF integrated with heterogeneous catalysis experiments for CO\(_2\) valorization in water.