Fixing CO 2 under Atmospheric Conditions and Dual Functional Heterogeneous Catalysis Employing Cu MOFs: Polymorphism, Single-Crystal-to-Single-Crystal (SCSC) Transformation and Magnetic Studies.

New copper compounds, [Cu(C 14 H 8 O 6 )(C 10 H 8 N 2 )(H 2 O)] ( 1 ), [Cu(C 14 H 8 O 6 )(C 10 H 8 N 2 )(H 2 O)]·(C 3 H 7 ON) 2 ( 2 ), [Cu(C 14 H 8 O 6 )(C 10 H 8 N 2 )(H 2 O) 2 ]·(C 3 H 7 ON) ( 3 ), [Cu(C 14 H 8 O 6 )(C 10 H 8 N 4 )] ( 4 ), and [Cu(C 14 H 8 O 6 )(C 10 H 8 N 4 )]·(H 2 O) ( 5 ), were prepared employing 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2,5-BPTA) as the primary ligand and 4,4'-bipyridine ( 1 - 3 ) and 4,4'-azopyridine ( 4 - 5 ) as the secondary ligands. Single-crystal studies indicated that compounds 1 - 4 have two-dimensional layer structures and compound 5 has a three-dimensional structure. Compounds 1 - 3 were isolated from the same reaction mixture but by varying the time of reaction. The framework structures of compounds 1 - 3 are similar and may be considered as polymorphic structures. Compounds 4 and 5 can also be considered polymorphic with a change in dimensionality of the structure. Compounds 1 - 3 can be formed through a single-crystal-to-single-crystal transformation under a suitable solvent mixture. The Cu center was explored for the Lewis acid-catalyzed cycloaddition reaction of epoxide and CO 2 under ambient conditions in a solventless condition and also for the synthesis of propargylamine derivatives by three-component coupling reactions (A 3 coupling) in a DCM medium. The Lewis basic functionality of the MOF (-N═N- group) has been explored for the Henry reaction (aldol condensation) in a solventless condition. In all of the catalytic reactions, good yields and recyclability were observed. The magnetic studies indicated that compounds 1 and 4 have antiferromagnetic interactions and compound 5 has ferromagnetic interactions. The present studies illustrated the rich diversity that the copper-containing compounds exhibit in extended framework structures.