Accessible microwave synthetized conjugated poly(azomethine‐pyridine) network and its metal complexes for CO₂conversion

Abstract

A conjugated crosslinked polyazomethine containing pyridine units (PAM-Py) was prepared from two commercial monomers, 2,6-diaminopyridine and isophthaldehyde, under microwave heating in only 30 min. Taking advantage of its thermal and chemical stability, porosity (S BET of 192 m 2 /g), insolubility, and ability to coordinate metals through the pyridine or imine N atoms, ruthenium-, aluminum-, iron-, and cobalt-poly(azomethine-pyridine) complexes (PAM-PyM) were prepared. The resulting metal polymers were evaluated as heterogeneous catalysts for the cycloaddition of CO 2 to epoxides yielding selectively the corresponding cyclic carbonates. All heterogeneous catalysts showed an extraordinary effectiveness with very high yields of epoxide conversion (up to 98%), turnover numbers up to 7425, and were reused at least five times without loss in catalytic activity.

Conversion of CO2 into Chloropropene Carbonate Catalyzed by Iron (II) Phthalocyanine Hypercrosslinked Porous Organic Polymer

“…These results indicated an important cooperative effect between the FePc-POP catalysts and the base, since together yielded the highest conversion. This cooperative effect was previously reported for other metal heterogeneous catalyst-DMAP systems [ 12 , 13 , 14 , 36 ]. Additionally, the reaction was carried out using FePc as homogeneous catalyst (entry 7).…”

“…However, iron could be considered as the optimum choice from a sustainable approach because it is cheap, earth abundant, and has relatively low toxicity [ 8 ]. Thus, in the last few years, some heterogeneous iron catalysts, that effectively promote this reaction, have been reported, e.g., iron doped mesoporous zeolites [ 9 , 10 ], a porous covalent triazine-based polymer containing iron oxide nanoparticles [ 11 ] and some iron-based poly(azomethine)s [ 12 , 13 , 14 ]. All reactions carried out with iron-containing heterogeneous catalysts produced cyclic carbonates in high yields, using CO 2 pressures between 3 and 20 bar and reaction temperatures in the range of 50–120 °C [ 9 , 10 , 11 , 12 , 13 , 14 ].…”

“…Thus, in the last few years, some heterogeneous iron catalysts, that effectively promote this reaction, have been reported, e.g., iron doped mesoporous zeolites [ 9 , 10 ], a porous covalent triazine-based polymer containing iron oxide nanoparticles [ 11 ] and some iron-based poly(azomethine)s [ 12 , 13 , 14 ]. All reactions carried out with iron-containing heterogeneous catalysts produced cyclic carbonates in high yields, using CO 2 pressures between 3 and 20 bar and reaction temperatures in the range of 50–120 °C [ 9 , 10 , 11 , 12 , 13 , 14 ]. The use of metal containing porous organic polymers (POPs) for this application offer some advantages over other materials because, in addition to their tailored porosity, they have an affinity for CO 2 and a predominant covalent character which offers high thermal and chemical stability [ 15 ].…”

New poly(ionic liquid)s based on poly(azomethine-pyridinium) salts and its use as heterogeneous catalysts for CO2 conversion

“…The novel polymers were completely insoluble and were used as heterogeneous catalysts in the above reaction working in relative soft conditions: 7 atm of CO2, 100°C, solvent-free and using very little amount of catalysts which implies high turnover numbers [27]. The presence of ionic groups in poly(azomethine-pyridine) networks could yield interesting heterogeneous catalysts that combine the properties of both.…”

“…Thus, isophtaldehyde and DA-PyMe (TFSI) were dissolved in a mixture of N-methylpyrrolidone (NMP) and N,N-dimethylpropylene urea (DMPU) and the mixture was stirred under nitrogen atmosphere for 20 min. A mixture of NMP and DMPU was chosen to carry out the reaction because in a previous work reported by us 2,6-diaminopyridine and isophthaldehyde was heated in this mixture of solvents under microwave irradiation yielding an insoluble and cross-linked polyazomethine network[27]. Then LiCl was added and the mixture was heated during 30 min under microwave at 180 °C.…”