New Eco-Friendly Phosphorus Organic Polymers as Gas Storage Media

Abstract

Three phosphate esters 1– 3 were successfully synthesized from the reaction of 2-, 3- and 4-hydroxybenzaldehyde with phosphoryl chloride. Reactions of 1– 3 with benzidine in the presence of glacial acetic acid gave the corresponding novel phosphorus organic polymers 4– 6 containing the azomethane linkage. The structures of the synthesized compounds were confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance and elemental analysis. Interesting physiochemical properties for the polymeric materials 4– 6 were observed using a combination of several techniques such as gel permeation chromatography, scanning electron microscopy, Brunauer–Emmett–Teller and nitrogen adsorption–desorption isotherm, Barrett–Joyner–Halenda and H-sorb 2600 analyzer. The mesoporous polymers 4– 6 exhibit tunable porosity with Brunauer–Emmett–Teller surface area (SA _BET = 24.8–30 m ²·g ^–1), pore volume (0.03–0.05 cm ³·g ^–1) and narrow pore size distribution, in which the average pore size was 2.4–2.8 nm. Polymers 4– 6 were found to have high gas storage capacity and physico-chemical stability, particularly at a high pressure. At 323 K and 50 bars, polymers 4– 6 have remarkable carbon dioxide uptake (up to 82.1 cm ³·g ^–1) and a low hydrogen uptake (up to 7.4 cm ³·g ^–1). The adsorption capacity of gasses for polymer 5 was found to be higher than those for polymers 4 and 6.