A heterometallic metal-organic framework based on multi-nuclear clusters exhibiting high stability and selective gas adsorption

The design and synthesis of porous heterometallic metal-organic frameworks (MOFs) with high thermal and chemical stability is a challenging task at present. In this work, by the heterometallic cooperative crystallization (HCC) approach, an original heterometallic MOF based on a tetra-carboxylic ligand has been solvothermally synthesized [In 6 O 3 Tb 3 O(CBDA) 3 ]·18DMF·3H 2 O ( In/Tb-CBDA ) [CBDA = 5,5′-(carbonylbis(azanediyl))-diisophthalic acid, DMF = N , N -dimethylformamide]. The framework of In/Tb-CBDA is cooperatively assembled from the rarely reported tetra-nuclear In 4 O 2 (COO) 4 and tri-nuclear Tb 3 O(COO) 6 clusters, and an organic ligand. Topological analysis indicates that In/Tb-CBDA exhibits a new (4,4,6)-connected topology with the Schläfli symbol (4·6 3 ·8 2 ) 6 (4 3 ·6 9 ·8 3 ) 2 (6 2 ·8 4 ) 3 . Noteworthy, forming multi-nuclear metal clusters prompts the framework to maintain high stability under the conditions of heating to 150 °C, exposure to air, and soaking in acidic and basic aqueous solutions for 12 h. After desolvation, In/Tb-CBDA shows permanent porosity proved by N 2 adsorption isotherms. In addition, theoretical ideal adsorption solution theory (IAST) calculation indicates that In/Tb-CBDA displayed high selective adsorption of CO 2 /CH 4 , C 2 H 6 /CH 4 and C 3 H 8 /CH 4 at room temperature. This work shows a striking example of a porous heterometallic MOF material with high thermal and chemical stability, which exhibits high-efficiency selective gas adsorption behaviour. Porous In/Tb-CBDA has been successfully synthesized in the light of the heterometallic cooperative crystallization (HCC) approach. In/Tb-CBDA with high thermal and chemical stability exhibited high performance for gas storage and separation.