*4.1. Synthesis*

Compounds (**1**) {[La2Cu3(μ-H2O)(ODA)6(H2O)3]·3H2O}n (LaCuODA) and (**2**) {[La2Co3(ODA)6 (H2O)6]·12H2O}n (LaCoODA)) have been previously reported [43,44] and were prepared accordingly, with slight modifications of the synthetic route. Complex (**1**) was synthesized by direct reaction of stoichiometric amounts of LaCl3·7H2O (0.37 g, 1.0 mmol), CuCl2·2H2O (0.20 g, 1.5 mmol), and oxydiacetic acid 0.40 g, 3.0 mmol). Reagents were dissolved in water (*ca*. 35 mL); pH was adjusted with diluted ammonia to 5–6. Light blue crystals of the complex appeared after 2–3 weeks. These were separated by filtration and washed twice with water. Complex (**2**) was prepared starting from La2O3 (98 mg, 0.3 mmol), Co(COOCH3)2·4H2O (224 mg, 0.9 mmol), and oxydiacetic acid (322 mg, 2.4 mmol). Then, 30 mL water was added, and the mixture was placed in a Teflon-lined 45 mL stainless steel acid digestion vessel and heated at 120 ◦C for 45 h. The resulting solution was filtered, and the filtrate was allowed to stand at room temperature. After five days, a pale red polycrystalline solid appeared. It was filtered and washed twice with water.

The purity of the solids was checked by elemental analysis (C, H) and IR spectroscopy.

Calculated for La2Cu3C24H38O37 (1), C, 20.8; H, 2.8. Found, C, 21.2; H, 2.9%.

Calculated for La2Co3C24H60O48 (2): C, 18.3; H, 4.0. Found: C, 18.5; H, 4.2%.

IR spectra were almost identical for both complexes, and can be used as a quick control of the purity of the compounds. The shift of νCOO (1724, 1419 cm<sup>−</sup>1) of the free ligand to *ca.* 1600 and 1430 cm<sup>−</sup><sup>1</sup> is noticeable. Besides, upon complexation, νCOC ( 1149 cm<sup>−</sup><sup>1</sup> ) for the free ligand shifts to *ca.* 1120 cm<sup>−</sup><sup>1</sup> (see Supplementary Information Figure S1a,b).

#### *4.2. Surface Area Determination*

The specific surface area (SBET) was measured by CO2 sorption measurement at 273 K, using Micrometrics 3 Flex equipment. Prior to the measurements, the samples were outgassed at 250 ◦C for 2 h. The BET surface area was estimated from the adsorption branch of the isotherms in the range 0.05 ≤ P/P ≤ 0.15. Additionally, the surface area was also estimated using the Langmuir equation. The average pore diameter was calculated using the DFT method, applied to the CO2 adsorption isotherm (Figures S2 and S3).
