Flexible Metal–Organic Framework-Bacterial Cellulose Nanocomposite for Iodine Capture

A flexible nanocomposite pellicle consisting of bacterial cellulose (BC) and zeolitic imidazolate framework-8 (ZIF-8) nanoparticles was prepared by sequentially soaking the BC pellicle in zinc ion and 2-methylimidazole (2-MI) solutions. The quality and quantity of ZIF-8 <i>in situ</i> crystallized in the pellicle was significantly improved when polydopamine, oxidatively self-polymerized dopamine, coating was applied prior on the surface of BC nanofibers. The polydopamine coating not only insulates the cellulose structure from competitive complex interaction with zinc ions employed for ZIF-8 formation but also can provide a photothermal feature to the ZIF-BC composite. ZIF-8 was well embedded inside the BC pellicle with a uniform shape and size of about 127 nm. Approximately, 70% (w/w) of the as-prepared nanocomposite (BC@Dopa-ZIF) is ZIF-8, which demonstrated a high iodine uptake capacity from vapor (1.87 ± 0.18 g I₂/g) and aqueous I₂/KI solution (1.31 ± 0.02 g I₂/g). The iodine captured by BC@Dopa-ZIF could be effectively released by irradiation of laser light of 808 nm due to the photothermal effect. The photothermal regeneration made BC@Dopa-ZIF maintain 99% and 87% of its initial iodine uptake capacity at the second and sixth use, respectively