Light Triggered Pore Size Tuning in Photoswitching Covalent Triazine Frameworks for Low Energy CO₂ Capture

Recently, photo switching porous materials have been widely reported for low energy costed CO₂ capture and release via simply remoted light controlling method. However, most reported photo responsive CO₂ adsorbents relied on metal organic framework (MOFs) functionalisation with photochromic moieties, and MOF adsorbents still suffered from chemically and thermally unstable issues. Thus, further metal free and highly stable organic photoresponsive adsorbents are necessary to be developed. CTFs, because of their high porosity and stability, have attracted great attention for CO₂ capture. Considering the high CO₂ uptake capacity and structural tunability of CTFs, it suggests high potential to fabricate the photoswitching CTF materials by the same functionalisation method as MOFs. Herein, the first series of photo switching CTFs were developed for low energy CO₂ capture and release. Apart from that, the CO₂ switching efficiency could be doubled either through the azobenzene numbers adjusting method or through the previously reported structural alleviation strategy. Furthermore, the pore size distribution of azobenzene functionalised PCTFs also could be tuned under UV exposure, which may contribute to the UV light induced decrease of CO₂ uptake capacity. These photoswitching CTFs represented a new kind of porous polymers for low energy costed CO₂ capture.