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

Abstract

New copper compounds, [Cu(C14H8O6)(C10H8N2)(H2O)] (1), [Cu(C14H8O6)(C10H8N2)(H2O)]·(C3H7ON)2 (2), [Cu(C14H8O6)(C10H8N2)(H2O)2]·(C3H7ON) (3), [Cu(C14H8O6)(C10H8N4)] (4), and [Cu(C14H8O6)(C10H8N4)]·(H2O) (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 CO2 under ambient conditions in a solventless condition and also for the synthesis of propargylamine derivatives by three-component coupling reactions (A3 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.

Synergistic Induction of Solvent and Ligand-Substitution in Single-Crystal to Single-Crystal Transformations toward a MOF with Photocatalytic Dye Degradation

“…Even though there are various examples of water-induced SCSC transformations reported up to date, this synergistic induction along with ligand-substitution is, however, relatively rare. Most of the water-triggered SCSC transformations involve dehydration/rehydration in which the water molecule played its role as ligand and/or guest molecules. − The completion of the 1a → 1b and 2a → 2b SCSC transformations was studied by PXRD (see Figure a,b). In addition, the BET (Brunauer–Emmett–Teller) surface areas of 1a , 1b , 2a , and 2b were determined to be 1.17, 4.70, 2.28, and 4.41 m 2 /g, respectively.…”

Turn-off luminescence sensing, white light emission and magnetic studies of two-dimensional lanthanide MOFs

“…The UV-Vis absorption spectra indicated bands corresponding to the π–π* and n–π* transitions of the ligands 2,5-BPTA, 2,2′-bipyridine and 1,10-phenanthroline. 60,61 The spectra exhibited a red shift in the absorption of the π–π* and n–π* transitions in the metalated compounds (Fig. S6 and Table S6†).…”

Bifunctional MOFs in Heterogeneous Catalysis

“…(b) Possible mechanism for the formation of cyclic carbonate. Reproduced with permission from ref . Copyright 2023 American Chemical Society.…”

“…244 A copper MOF, [Cu(2,5-BPTA)(bpy)(H 2 O)] (2,5-BPTA = 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid and bpy = 4,4′-bipyridine, Figure 10a), was shown to catalyze CO 2 to cyclic carbonates in the presence of TBAB as a cocatalyst. 245 The Cu 2+ ions acts as the Lewis acid centers to polarize the epoxide oxygen and increase the electrophilicity of the carbon. The Br − from the TBAB helps in the ring opening of the epoxides.…”

“…The Cu 2+ acts as the center for the subsequent binding of CO 2 with the ring opened epoxide along with the elimination of the Br − by ring closing, forming the cyclic carbonates (Figure 10b). 245 As noted in Table 8, the number of examples of the conversion of CO 2 to cyclic carbonates are many. It appears that the presence of stronger acidic sites along with basic sites helps toward catalyzing this reaction.…”