Process for the hydrothermal preparation of a solid made up of a metal-organic network of porous and crystallised aluminium carboxylates, comprising at least the following steps: (i) mixing in an aqueous solvent: - at least one inorganic metal precursor in the form of metal Al, a metal salt Al 3+ or a coordination complex comprising the metal ion Al 3+; and - at least one organic precursor of ligand L, L being a tri- or tetra-carboxylate ligand of formula R 0 (COO-) q wherein R 0 represents • a mono- or poly-cyclic aryl radical, fused or not, comprising from 6 to 50 carbon atoms, • a mono- or poly-cyclic heteroaryl radical, fused or not, comprising from 4 to 50 carbon atoms, the radical R 0 being optionally substituted by one or more groups independently selected from the group comprising C 1-10 alkyl, C 2-10 alkene, C 2-10 alkyne, C 3-10 cycloalkyl, C 1-10 heteroalkyl, C 1-10 haloalkyl, C 6-10 aryl, C 3-20 heterocyclic, C 1-10 alkylC 6-10 aryl, C 1-10 alkylC 3-10 heteroaryl, F, Cl, Br, I, -NO 2, -CN, -CF 3, -CH 2 CF 3, -OH, -CH 2 OH, - CH 2 CH 2 OH, -NH 2, -CH 2 NH 2, -NHCHO, -COOH, -CONH 2, -SO 3 H, - PO 3 H 2, • q = 3 to 4; (ii) adjusting the pH of the mixture between 0.4 and 0.7, and (iii) heating the mixture obtained in (ii) for a period of 1 to 24 hours, to a temperature above 130°C so as to obtain said solid, and wherein in step (i) the inorganic metal precursor and the organic precursor of ligand L are mixed in a molar ratio between 1 and 5. (i) mixing in an aqueous solvent: - at least one inorganic metal precursor in the form of metal Al, a metal salt Al 3+ or a coordination complex comprising the metal ion Al 3+; and - at least one organic precursor of ligand L, L being a tri- or tetra-carboxylate ligand of formula R 0 (COO-) q wherein R 0 represents • a mono- or poly-cyclic aryl radical, fused or not, comprising from 6 to 50 carbon atoms, • a mono- or poly-cyclic heteroaryl radical, fused or not, comprising from 4 to 50 carbon atoms, the radical R 0 being optionally substituted by one or more groups independently selected from the group comprising C 1-10 alkyl, C 2-10 alkene, C 2-10 alkyne, C 3-10 cycloalkyl, C 1-10 heteroalkyl, C 1-10 haloalkyl, C 6-10 aryl, C 3-20 heterocyclic, C 1-10 alkylC 6-10 aryl, C 1-10 alkylC 3-10 heteroaryl, F, Cl, Br, I, -NO 2, -CN, -CF 3, -CH 2 CF 3, -OH, -CH 2 OH, - CH 2 CH 2 OH, -NH 2, -CH 2 NH 2, -NHCHO, -COOH, -CONH 2, -SO 3 H, - PO 3 H 2, • q = 3 to 4; - at least one inorganic metal precursor in the form of metal Al, a metal salt Al 3+ or a coordination complex comprising the metal ion Al 3+; and - at least one organic precursor of ligand L, L being a tri- or tetra-carboxylate ligand of formula R 0 (COO-) q wherein R 0 represents • a mono- or poly-cyclic aryl radical, fused or not, comprising from 6 to 50 carbon atoms, • a mono- or poly-cyclic heteroaryl radical, fused or not, comprising from 4 to 50 carbon atoms, the radical R 0 being optionally substituted by one or more groups independently selected from the group comprising C 1-10 alkyl, C 2-10 alkene, C 2-10 alkyne, C 3-10 cycloalkyl, C 1-10 heteroalkyl, C 1-10 haloalkyl, C 6-10 aryl, C 3-20 heterocyclic, C 1-10 alkylC 6-10 aryl, C 1-10 alkylC 3-10 heteroaryl, F, Cl, Br, I, -NO 2, -CN, -CF 3, -CH 2 CF 3, -OH, -CH 2 OH, - CH 2 CH 2 OH, -NH 2, -CH 2 NH 2, -NHCHO, -COOH, -CONH 2, -SO 3 H, - PO 3 H 2, • q = 3 to 4; • a mono- or poly-cyclic aryl radical, fused or not, comprising from 6 to 50 carbon atoms, • a mono- or poly-cyclic heteroaryl radical, fused or not, comprising from 4 to 50 carbon atoms, the radical R 0 being optionally substituted by one or more groups independently selected from the group comprising C 1-10 alkyl, C 2-10 alkene, C 2-10 alkyne, C 3-10 cycloalkyl, C 1-10 heteroalkyl, C 1-10 haloalkyl, C 6-10 aryl, C 3-20 heterocyclic, C 1-10 alkylC 6-10 aryl, C 1-10 alkylC 3-10 heteroaryl, F, Cl, Br, I, -NO 2, -CN, -CF 3, -CH 2 CF 3, -OH, -CH 2 OH, - CH 2 CH 2 OH, -NH 2, -CH 2 NH 2, -NHCHO, -COOH, -CONH 2, -SO 3 H, - PO 3 H 2, • q = 3 to 4; (ii) adjusting the pH of the mixture between 0.4 and 0.7, and (iii) heating the mixture obtained in (ii) for a period of 1 to 24 hours, to a temperature above 130°C so as to obtain said solid, and wherein in step (i) the inorganic metal precursor and the organic precursor of ligand L are mixed in a molar ratio between 1 and 5.