UV-Rearranged PIM-1 Polymeric Membranes for Advanced Hydrogen Purification and Production

• Published in: Advanced energy materials 2012-12, Vol.2 (12), p.1456-1466
• Main Authors: Li, Fu Yun, Xiao, Youchang, Ong, Yee Kang, Chung, Tai-Shung
• Format: Article
• Language: English
• Subjects: 1,2‐migration reaction; 2-migration reaction; gas separation; hydrogen; Permeability; polymers of intrinsic microporosity (PIM-1) membranes; Sunscreen; Ultraviolet radiation; UV-rearranged
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.201200296

Polymers of intrinsic microporosity (PIM‐1) have been known for their super high permeability but average selectivity for medium‐size gas pairs. They have unimpressive selectivity for H2 and CO2 separation (i.e., α (H2/CO2) = 0.6). For the first time, we have discovered that ultraviolet (UV)‐rearranged polymers of PIM‐1 membranes can be used for H2/CO2 separation with far superior separation performance to others in literatures. The PIM‐1 membrane after UV radiation for 4 hours shows H2 permeability of 452 barrer with H2/CO2 selectivity of 7.3. Experimental data and molecular simulation reveal that the polymer chains of PIM‐1 undergo 1,2‐migration reaction and transform to close‐to‐planar like rearranged structure after UV radiation. As a result, the UV‐irradiated PIM‐1 membrane shows considerable drops in both fractional free volume (FFV) and size of micro‐pores. Positron annihilation lifetime (PAL) results have confirmed the chemical and structural changes, suggesting the FFV and pore size drops are mainly ascribed to the destructed spiro‐carbon centre during UV radiation. Sorption and x‐ray diffractor (XRD) analyses indicate that the impressive H2/CO2 selectivity arises from the significantly enhanced diffusivity selectivity induced by UV radiation, followed by molecular rearrangement, conformation change and chain packing. The polymer chains of PIM‐1 undergo 1,2‐migration reaction and transform to close‐to‐planar like rearranged structure after ultraviolet (UV) irradiation. As a result, the UV‐irradiated PIM‐1 membrane shows considerable drops in both fractional free volume (FFV) and size of micro‐pores. The resultant PIM‐1 membranes are used for H2/CO2 separation and reveal far superior separation performance to others in the literature.