Salt-templated porous melamine-based conjugated polymers for selective oxidation of amines into imines under visible light

Conjugated polymers have a broad application foreground in the field of photocatalytic organic synthesis to produce value-added chemicals due to their functional diversity, broad light responsive ability, high thermal and chemical stability, and tunable band structure. Herein, using mixed chloride salts (i.e., NaCl/LiCl) as building template, a series of porous conjugated polymers constructed by melamine and terephthalaldehyde monomers were obtained through a Schiff-base reaction in the absence of any exter-nal solvent. Melamine-terephthalaldehyde polymer (i.e., PMTPA-x, x represents the mass ratio of salt -mixture to mixed precursors of PMTPA) materials displayed porous morphologies and possessed different energy band structures via regulating the mass ratio of mixed-salt to monomers. Specifically, PMTPA-20 has a larger specific surface area and more suitable redox potential towards the photocatalytic oxidative coupling of amines to imines. Under visible light, with molecular oxygen as oxidant, PMTPA-20 achieves 97% conversion of benzylamine in 8 h which is 3.9 times higher than that of pristine PMTPA (25% conver-sion in 8 h). In addition, PMTPA-20 catalyst has good structure stability and reusability performance for photocatalytic reactions.(c) 2022 Elsevier Inc. All rights reserved.

Automated summary

A series of porous conjugated polymers were synthesized using mixed chloride salts as a template. The polymer materials displayed porous morphologies and different energy band structures by regulating the mass ratio of salts to monomers. Among them, PMTPA-20 exhibited a larger specific surface area and suitable redox potential for the photocatalytic oxidative coupling reaction. With molecular oxygen as the oxidant, PMTPA-20 achieved a conversion rate of 97% for benzylamine in 8 hours, which was 3.9 times higher than that of pristine PMTPA. Furthermore, PMTPA-20 catalyst showed good structural stability and reusability for photocatalytic reactions.