Fixing CO2 under Atmospheric Conditions and Dual Functional Heterogeneous Catalysis Employing Cu MOFs: Polymorphism, Single-Crystal-to-Single-Crystal (SCSC) Transformation and Magnetic Studies

New Cu MOFs have been shown to exhibit polymorphism, CO2 fixation to cyclic carbonates, A(3) coupling (Lewisacid catalysis), Henry aldol condensation (Lewis base catalysis),and interesting magnetic behavior. New copper compounds, [Cu(C14H8O6)(C10H8N2)(H2O)] (1), [Cu(C14H8O6)(C10H8N2)(H2O)]& BULL;(C3H7ON)(2) (2), [Cu(C14H8O6)(C10H8N2)(H2O)(2)]& BULL;(C3H7ON)(3), [Cu(C14H8O6)(C10H8N4)] (4), and [Cu(C14H8O6)(C10H8N4)]& BULL;(H2O) (5), were prepared employing2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2,5-BPTA) as the primaryligand and 4,4 & PRIME;-bipyridine (1-3) and 4,4 & PRIME;-azopyridine (4-5) as the secondary ligands. Single-crystal studies indicated thatcompounds 1-4 have two-dimensionallayer structures and compound 5 has a three-dimensionalstructure. Compounds 1-3 were isolatedfrom 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 consideredpolymorphic with a change in dimensionality of the structure. Compounds 1-3 can be formed through a single-crystal-to-single-crystaltransformation under a suitable solvent mixture. The Cu center wasexplored for the Lewis acid-catalyzed cycloaddition reaction of epoxideand CO2 under ambient conditions in a solventless conditionand also for the synthesis of propargylamine derivatives by three-componentcoupling reactions (A(3) coupling) in a DCM medium. The Lewisbasic functionality of the MOF (-N UN- group)has been explored for the Henry reaction (aldol condensation) in asolventless condition. In all of the catalytic reactions, good yieldsand recyclability were observed. The magnetic studies indicated thatcompounds 1 and 4 have antiferromagneticinteractions and compound 5 has ferromagnetic interactions.The present studies illustrated the rich diversity that the copper-containingcompounds exhibit in extended framework structures.