Synthesis of Nitrogen-Rich Polymers by Click Polymerization Reaction and Gas Sorption Property

Abstract

Microporous organic polymers (MOPs) are promising materials for gas sorption because of their intrinsic and permanent porosity, designable framework, and low density. The introduction of nitrogen-rich building block in MOPs will greatly enhance the gas sorption capacity. Here, we report the synthesis of MOPs from the 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine unit and aromatic azides linkers by click polymerization reaction. Fourier transform infrared (FTIR) and solid-state ¹³C CP-MAS (Cross Polarization-Magic Angle Spinning) NMR confirm the formation of the polymers. CMOP-1 and CMOP-2 exhibit microporous networks with a BET (Brunauer–Emmett–Teller) surface area of 431 m²·g⁻¹ and 406 m²·g⁻¹ and a narrow pore size distribution under 1.2 nm. Gas sorption isotherms including CO₂ and H₂ were measured. CMOP-1 stores a superior CO₂ level of 1.85 mmol·g⁻¹ at 273 K/1.0 bar, and an H₂ uptake of up to 2.94 mmol·g⁻¹ at 77 K/1.0 bar, while CMOP-2, with its smaller surface area, shows a lower CO₂ adsorption capacity of 1.64 mmol·g⁻¹ and an H₂ uptake of 2.48 mmol·g⁻¹. In addition, I₂ vapor adsorption was tested at 353 K. CMOP-1 shows a higher gravimetric load of 160 wt%. Despite the moderate surface area, the CMOPs display excellent sorption ability for CO₂ and I₂ due to the nitrogen-rich content in the polymers.