Compound characterization data — Bhat et al., 2026

Samiha Bhat, Rachel A. Yang, Camilo A. Ortega-Vega, Rafat H. Aunkon, Miguel Sepúlveda-Pagán, Kai Sun, Anatoly I. Frenkel, Yomaira J. Pagán-Torres, Eranda Nikolla. “Reversible modulation of metal active site ensembles within doped perovskite oxides to drive switchable catalytic outcomes.” ChemRxiv (2026). https://doi.org/10.26434/chemrxiv.15007470/v1

Undoped, doped, exsolved, and supported catalysts
ICP-MS, Rh content in doped and exsolved catalysts	2.2 ± 0.5 wt. %
ICP-MS, Rh loading in supported controls	1 wt.% Rh/SrTiO3 and 2.5 wt.% Rh/SrTiO3
PXRD	All samples exhibited diffractograms characteristic of cubic perovskite structures
Raman spectroscopy, Rh-doped SrTiO3	First-order Raman scattering peaks centered at 532 cm⁻¹ and 795 cm⁻¹, corresponding to the TO4 and LO4 phonon branches respectively
Raman spectroscopy, bare SrTiO3 and 1 wt.% Rh/SrTiO3	First-order Raman scattering peaks centered at 532 cm⁻¹ and 795 cm⁻¹ were not observed
BET surface area, SrTiO3	27 ± 5 m² gcat⁻¹
BET surface area, 2.5 wt.% Rh/SrTiO3	30 ± 5 m² gcat⁻¹
BET surface area, Rh-doped SrTiO3	31 ± 5 m² gcat⁻¹
BET surface area, Exs600-Rh-SrTiO3	29 ± 5 m² gcat⁻¹
BET surface area, Exs800-Rh-SrTiO3	25 ± 5 m² gcat⁻¹

Rh-doped and exsolved SrTiO3 catalysts
In situ STEM-HAADF, Rh-doped SrTiO3 heated at 450 °C under vacuum	uniform arrays of Sr and Ti atoms consistent with the cubic perovskite structure; d(110) = 0.28 nm
In situ STEM-HAADF, Exs600-Rh-SrTiO3 heated at 450 °C under vacuum	distinct Rh cluster formation, with nanoparticle clusters partially embedded in the parent perovskite lattice; average Rh NP diameter 1.5 ± 0.2 nm; (110) interplanar spacing 0.27 nm; adjacent (111) plane fringe spacing for the exsolved Rh NP approximately 0.23 nm
In situ STEM-HAADF, Exs800-Rh-SrTiO3 heated at 450 °C under vacuum	distinct Rh cluster formation, with nanoparticle clusters partially embedded in the parent perovskite lattice; average Rh NP diameter 2.0 ± 0.4 nm; (110) interplanar spacing 0.27 nm; adjacent (111) plane fringe spacing for the exsolved Rh NP approximately 0.23 nm
EELS mapping, exsolved nanoparticles	nanoparticles were composed exclusively of Rh, while Sr, Ti, and O signals remained uniformly distributed within the surrounding perovskite lattice
CO-DRIFTS, as-synthesized Rh-doped SrTiO3	symmetric and asymmetric Rh+-(CO)2 gem-dicarbonyl species centered between 2090–2084 cm⁻¹ and ~2020 cm⁻¹, respectively
CO-DRIFTS, reduced Rh-doped SrTiO3	additional vibrational modes corresponding to linear Rh0-CO species between 2070–2050 cm⁻¹; Rh gem-dicarbonyl features persisted
CO pulsing and CO-DRIFTS, as-synthesized Rh-doped SrTiO3	CO pulse 17.12 ± 0.1 µmolCO gcat⁻¹; νlinear/νs N/A due to absence of linear CO vibrational features; surface Rh 8.56 ± 0.1 µmolsurfaceRh gcat⁻¹
CO pulsing and CO-DRIFTS, Rh-doped SrTiO3 after H2 pretreatment at 450 °C for 2 h	CO pulse 17.49 ± 0.1 µmolCO gcat⁻¹; νlinear/νs 1 ± 0.8; surface Rh 12.94 ± 0.1 µmolsurfaceRh gcat⁻¹
CO pulsing and CO-DRIFTS, Exs600-Rh-SrTiO3 after H2 pretreatment at 450 °C for 2 h	CO pulse 12.70 ± 0.7 µmolCO gcat⁻¹; νlinear/νs 3 ± 2.0; surface Rh 10.58 ± 0.7 µmolsurfaceRh gcat⁻¹
CO pulsing and CO-DRIFTS, Exs800-Rh-SrTiO3 after H2 pretreatment at 450 °C for 2 h	CO pulse 10.59 ± 0.6 µmolCO gcat⁻¹; νlinear/νs 17 ± 2.3; surface Rh 10.24 ± 0.6 µmolsurfaceRh gcat⁻¹

Rh-doped SrTiO3 and Exs800-Rh-SrTiO3
Rh K-edge EXAFS fit, as-synthesized Rh-doped SrTiO3 analyzed at 25 °C	Rh-O (SS): CN 6.6 ± 1.1, bond length 2.010 ± 0.012 Å, σ2 0.0019 ± 0.0017 Å², ΔE0 −3.6 ± 2.0 eV; Rh-Ti (SS): 5.3 ± 2.3, 3.863 ± 0.029 Å, 0.0062 ± 0.0036 Å², −3.3 ± 3.1 eV; Rh-O-Ti (DS): 10.6 (fixed), 3.863 Å (fixed), 0.0062 Å² (fixed), −3.3 eV (fixed); Rh-O-Ti-O (TS): 5.3 (fixed), 3.863 Å (fixed), 0.0062 Å² (fixed), −3.3 eV (fixed)
Rh K-edge EXAFS fit, Rh-doped SrTiO3 in situ reduced and analyzed at 450 °C under H2 for 2 h	Rh-Rh (SS): CN 0.3 ± 0.5, bond length 2.647 ± 0.031 Å, σ2 0.0000 ± 0.0129 Å², ΔE0 −8.2 ± 1.7 eV; Rh-O (SS): 3.1 ± 0.4, 2.027 ± 0.010 Å, 0.0016 ± 0.0017 Å², −7.3 ± 1.6 eV; Rh-Ti (SS): 6.0 ± 1.8, 3.883 ± 0.022 Å, 0.0155 ± 0.0035 Å², −8.2 eV (fixed); Rh-O-Ti (DS): 12 (fixed), 3.883 Å (fixed), 0.0155 Å² (fixed), −8.2 eV (fixed); Rh-O-Ti-O (TS): 6.0 (fixed), 3.883 Å (fixed), 0.0155 Å² (fixed), −8.2 eV (fixed)
Rh K-edge EXAFS fit, Exs800-Rh-SrTiO3 ex situ exsolved at 800 °C under 10 % H2 for 10 h and analyzed at 25 °C	Rh–Rh (SS): CN 1.5 ± 0.8, bond length 2.657 ± 0.011 Å, σ2 0.0008 ± 0.0039 Å², ΔE0 −7.7 ± 1.7 eV; Rh–O (SS): 2.8 ± 0.6, 2.030 ± 0.018 Å, 0.0015 ± 0.0030 Å², −2.5 ± 2.6 eV; Rh–Ti (SS): 3.9 ± 1.5, 3.851 ± 0.019 Å, 0.0075 ± 0.0035 Å², −7.7 eV (fixed); Rh–O–Ti (DS): 7.8 (fixed), 3.851 Å (fixed), 0.0075 Å² (fixed), −7.7 eV (fixed); Rh–O–Ti-O (TS): 3.9 (fixed), 3.851 Å (fixed), 0.0075 Å² (fixed), −7.7 eV (fixed)
Rh K-edge EXAFS fit, Exs800-Rh-SrTiO3 in situ reduced and analyzed at 450 °C under H2 for 2 h	Rh-Rh (SS): CN 1.8 ± 0.8, bond length 2.675 ± 0.012 Å, σ2 0.0056 ± 0.0034 Å², ΔE0 −7.9 ± 1.3 eV; Rh-O (SS): 2.4 ± 0.4, 2.038 ± 0.013 Å, 0.0027 ± 0.0021 Å², −2.4 ± 1.8 eV; Rh-Ti (SS): 4.2 ± 1.7, 3.861 ± 0.019 Å, 0.0145 ± 0.0046 Å², −7.9 eV (fixed); Rh-O-Ti (DS): 8.4 (fixed), 3.861 Å (fixed), 0.0145 Å² (fixed), −7.9 eV (fixed); Rh-O-Ti-O (TS): 4.2 (fixed), 3.861 Å (fixed), 0.0145 Å² (fixed), −7.9 eV (fixed)

Doped, exsolved, and reincorporated perovskite
Rh K-edge EXAFS fit, as-synthesized doped perovskite analyzed at 25 °C	Rh-O (SS): CN 6.3 ± 1.6, bond length 1.999 ± 0.018 Å, σ2 0.0003 ± 0.0028 Å², ΔE0 −9.5 ± 3.0 eV; Rh-Ti (SS): 5.1 ± 2.9, 3.854 ± 0.038 Å, 0.0053 ± 0.0052 Å², −8.1 ± 3.9 eV; Rh-O-Ti (DS): 10.2 (fixed), 3.854 Å (fixed), 0.0053 Å² (fixed), −8.1 eV (fixed); Rh-O-Ti-O (TS): 5.1 (fixed), 3.854 Å (fixed), 0.0053 Å² (fixed), −8.1 eV (fixed)
Rh K-edge EXAFS fit, perovskite in situ exsolved and analyzed at 700 °C under H2 for 1 h	Rh-Rh (SS): CN 1.9 ± 1.0, bond length 2.688 ± 0.014 Å, σ2 0.0057 ± 0.0034 Å², ΔE0 −9.2 ± 2.0 eV; Rh-O (SS): 3.2 ± 0.8, 2.041 ± 0.022 Å, 0.0071 ± 0.0033 Å², −5.7 ± 3.0 eV; Rh-Ti (SS): 3.4 ± 2.1, 3.867 ± 0.030 Å, 0.0141 ± 0.0066 Å², −9.2 eV (fixed); Rh-O-Ti (DS): 6.8 (fixed), 3.867 Å (fixed), 0.0141 Å² (fixed), −9.2 eV (fixed); Rh-O-Ti-O (TS): 3.4 (fixed), 3.867 Å (fixed), 0.0141 Å² (fixed), −9.2 eV (fixed)
Rh K-edge EXAFS fit, perovskite in situ oxidized at 700 °C under O2 for 1 h and analyzed at 25 °C	Rh-O (SS): CN 5.8 ± 1.5, bond length 1.980 ± 0.019 Å, σ2 0.0000 ± 0.0031 Å², ΔE0 −9.4 ± 3.1 eV; Rh-Ti (SS): 5.3 ± 2.5, 3.855 ± 0.032 Å, 0.0037 ± 0.0046 Å², −7.5 ± 3.3 eV; Rh-O-Ti (DS): 10.6 (fixed), 3.855 Å (fixed), 0.0037 Å² (fixed), −7.5 eV (fixed); Rh-O-Ti-O (TS): 5.3 (fixed), 3.855 Å (fixed), 0.0037 Å² (fixed), −7.5 eV (fixed)

Infrared band assignments and wavenumbers for different vibrational modes of gaseous and surface species for CO2 hydrogenation on doped and exsolved catalysts
Methane (CH4)	3015 cm⁻¹; ν(C-H)
Bicarbonates (CO3-) and monodentate carbonates (CO32-)	1640 – 1600, 1440 – 1400, 1300 – 1200 cm⁻¹; ν(CO3δ-)
Formates (HCOO*)	1590, 1370 cm⁻¹; νas(OCO), νs(OCO); 2950, 2870, 2820 cm⁻¹; ν(C-H)
Formyls (HCO*)	2740, 2700 cm⁻¹; ν(C-H)
Carboxylates (COOH*)	1560, 1330 cm⁻¹; νas(OCO), νs(OCO)