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Flexible and thermally stable polyimide (PI) films containing a hierarchical surface structure were synthesized as substrates to support visible-light active cuprous oxide for photocatalytic reduction of carbon dioxide for the first time. With the nanocasting technique, the surface structure on the leaves of Xanthosoma sagittifolium was successfully duplicated on PI films. Followed by the ion-exchange process and adequate thermal treatment, cuprous oxide nanoparticles were successfully immobilized on the artificial PI leaves and exhibited the capability to photoreduce carbon dioxide into carbon monoxide under visible-light illumination. With the selection of biomimetic structures and adjustment of fabrication parameters, the hydrophobicity and optical absorption edge of the photocatalytic film were tunable. An increase in hydrophobicity improved the yield of carbon monoxide. The introduction of a hierarchical structure on the surface and cuprous oxide within the matrix dramatically enhanced the thermal stability of the PI film. The flexible photocatalytic film is a promising material for the applications requiring high mechanical and thermal stability, such as industrial flue-gas treatments.

Like the thigmonastic responses of the leaves of Mimosa pudica, the curling of organosoluble and free‐standing polyimide (PI) films under the stimuli of fingertip‐touching or air‐blowing is discovered for the first time. The authors discover that the PI films at the dry status can rapidly and reversibly attract and release water molecules at the interface of the thin film in response to the changes of environmental humidity. The moisture‐triggered heterogeneous deformation across the film leads to self‐curling of PI films. With the blending of suitable amounts of sulfonated‐polyaniline (PANI‐S) to the PI matrix, the resultant PANI‐S/PI film can more effectively breath water from the air and simultaneously create more significant deformation and faster recovery. With the suitable designed patterns on the film, it can serve a highly sensitive and reliable actuator to grasp and release subjects as well as to fold into 3D structures, and to roll like a tank tread by providing trace moisture gradients. This robust PANI‐S/PI film can be cast into any shape or coated on various substrates and thus is a promising material for smart delivery systems in industrial applications.

Three types of graphitic carbon nitride (gCN) nanosheets were derived from direct thermal condensation of urea, melamine, and dicyandiamide, respectively. As the sample (uCN) synthesized from urea exhibited porous morphology and highest surface area among other gCN, anatase TiO2 nanoparticles were then in-situ deposited on uCN via solvothermal process without further calcination. The resultant Ti/uCN_x samples remained with higher surface area and exhibited visible-light activity. The derived band structure of each sample also confirmed its ability to photoreduce CO2. XPS results revealed surface compositions of each sample. Those functional groups governed adsorption of reactant, interfacial interaction, electron transfer rate, and consequently influenced the yield of products. Carbon monoxide and methanol were detected from LED-lamp illuminated samples under appropriate moisture content. Samples with higher ratio of terminal amine groups produced more CO. The presence of hydroxyl groups promoted the initial conversion of methanol. The obtained Ti/uCN_0.5 and Ti/uCN_1.5 samples exhibited better quantum efficiency toward CO2 conversion and demonstrated stability to consistently produce CO under cycling photoreaction.