Artificial cellulosic leaf with adjustable enzymatic CO2 sequestration capability

Abstract

Developing artificial leaves to address the environmental burden of CO₂ is pivotal for advancing our Net Zero Future. In this study, we introduce EcoLeaf, an artificial leaf that closely mimics the characteristics of natural leaves. It harnesses visible light as its sole energy source and orchestrates the controlled expansion and contraction of stomata and the exchange of petiole materials to govern the rate of CO₂ sequestration from the atmosphere. Furthermore, EcoLeaf has a cellulose composition and mechanical strength similar to those of natural leaves, allowing it to seamlessly integrate into the ecosystem during use and participate in natural degradation and nutrient cycling processes at the end of its life. We propose that the carbon sequestration pathway within EcoLeaf is adaptable and can serve as a versatile biomimetic platform for diverse biogenic carbon sequestration pathways in the future.

Fig. 1. Preparation of EcoLeaf and its structural characterization.

a Construction and performance of EcoLeaf; b The detailed preparation process of EcoLeaf; SEM maps of light-responsive 3D mesh matrix (Isopropyl thioxanthone, ITX) (c) before grafting vs. (d) after grafting of cellulose substrate; Fluorescence spectra of (e) EcoLeaf without encapsulated CA vs. (f) EcoLeaf encapsulated with FITC-CA under LCSM (The experiment was repeated independently three times with similar results); C 1s core-level spectra and full spectra of (g) Cellulose paper (Cp), (h) Cellulose paper-isopropyl thioxanthone (Cp-ITX), and (i) EcoLeaf.

Fig. 2. Comparison of mechanical properties of natural blades vs. EcoLeaf.

a Natural leaves from Trachycarpus fortune (Tf), Cercis chinensis bunge (CcB), Pyrus ussuriensis (Pu), Zamioculcas zamiifolia engl (ZzE), Holly, and EcoLeaf (EL) respectively; b Stress-strain curves and c Young’s modulus of natural leaves from different sources and EcoLeaf (EL 1 thickness 0.19 mm and density 0.60 g/cm³, EL 2 thickness 0.22 mm and density 0.61 g/cm³) (Parallel experiments with three sets of identical samples, data are presented as mean values +/−SEM).

Fig. 3. Photothermal conversion performance of EcoLeaf.

Effects of K/S value and visible illuminance on (a) initial warming rate and (b) final arrival temperature of artificial leaves at an initial temperature of 30 °C.

Fig. 4. Light response characterization and stability of EcoLeaf.

a Schematic diagrams of the changes in the molecular structure of GMA/4,4’-AZO and the stomata of EcoLeaf under different wavelengths of excitation light; photoresponse properties of EcoLeaf under (b) 365 nm UV and (c) 450 nm visible excitation; d Changes in the pore volume, average pore size and surface area of EcoLeaf under 450 nm visible and 365 nm UV excitation; e Changes in the optical contact angle of EcoLeaf under 450 nm visible and 365 nm UV excitation (Parallel experiments with three sets of identical samples, data are presented as mean values +/−SEM); Effects of stomatal expansion and contraction characteristics on the (f) temperature stability and (g) pH stability of EcoLeaf.

Fig. 5. Material transport characteristics and carbon sequestration of EcoLeaf.

a Schematic diagram of the CO₂ capture device; b Effect of stomatal expansion and contraction states on the carbon capture performance of EcoLeaf (Parallel experiments with three sets of identical samples, data are presented as mean values +/−SEM); c Litmus color diagrams of EcoLeaf embedded with litmus test solution after CO₂ capture and litmus color diagrams of EcoLeaf after placing its petiole in deionized aqueous solution for transporting H₂CO₃ at a room temperature of 30 °C; d Changes in water content of EcoLeaf with and without water supply (365 nm and 450 nm) (Parallel experiments with three sets of identical samples); e Long-term carbon sequestration stability of EcoLeaf with and without water supply and cycling stability of EcoLeaf with water supply.

Fig. 6. Soil degradation characteristics of EcoLeaf.

a Soil degradation and mass loss of natural leaves and EcoLeaf at room temperature (Parallel experiments with three sets of identical samples, data are presented as mean values +/−SEM); b Soil eco-culture maps of natural leaves (A-1-A-2), EcoLeaf (B-1-B-2), and blank group (C-1-C-2) at room temperature.