With the continuous increase in fossil fuels consumption and the rapid growth of atmospheric CO2 concentration, the harmonious state between human and nature faces severe challenges. Exploring green and sustainable energy resources and devising efficient methods for CO2 capture, sequestration and utilization are urgently required. Converting CO2 into fuels/chemicals/materials as an indispensable element for CO2 capture, sequestration and utilization may offer a win-win strategy to both decrease the CO2 concentration and achieve the efficient exploitation of carbon resources. Among the current major methods (including chemical, photochemical, electrochemical and enzymatic methods), the enzymatic method, which is inspired by the CO2 metabolic process in cells, offers a green and potent alternative for efficient CO2 conversion due to its superior stereo-specificity and region/chemo-selectivity. Thus, in this tutorial review, we firstly provide a brief background about enzymatic conversion for CO2 capture, sequestration and utilization. Next, we depict six major routes of the CO2 metabolic process in cells, which are taken as the inspiration source for the construction of enzymatic systems in vitro. Next, we focus on the state-of-the-art routes for the catalytic conversion of CO2 by a single enzyme system and by a multienzyme system. Some emerging approaches and materials utilized for constructing single-enzyme/multienzyme systems to enhance the catalytic activity/stability will be highlighted. Finally, a summary about the current advances and the future perspectives of the enzymatic conversion of CO2 will be presented.

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A novel approach combining layer‐by‐layer (LbL) assembly with biomimetic mineralization is proposed to prepare protamine–titiania hybrid microcapsules. More specifically, these microcapsules are fabricated by alternative deposition of positively charged protamine layers and negatively charged titania layers on the surface of CaCO3 microparticles, followed by dissolution of the CaCO3 microparticles using EDTA. During the deposition process, the protamine layer induces the hydrolysis and condensation of a titania precursor, to form the titania layer. Thereafter, the negatively charged titania layer allows a new cycle of deposition step of the protamine layer, which ensures a continuous LbL process. The morphology, structure, and chemical composition of the microcapsules are characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, and X‐ray photoelectron spectroscopy. Moreover, these protamine–titania hybrid microcapsules are first employed as the carrier for the immobilization of yeast alcohol dehydrogenase (YADH), and the encapsulated YADH displays enhanced recycling stability. This approach may open a facile, general, and efficient way to prepare organic–inorganic hybrid materials with different compositions and shapes.

Protamine, a kind of cationic protein extracted from sperm nuclei, was employed for the first time in vitro to induce the formation of a titania/protamine nanoparticle composite from a water-stable titanium precursor, titanium(IV) bis(ammonium lactato) dihydroxide (Ti-BALDH). The resulting titania/protamine nanoparticle composite was extensively characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The titania/protamine nanoparticle composite was of amorphous structure, and exhibited a different morphology from those prepared by an alkali-catalyzed approach. The catalyzing and templating function of protamine involved in the synthesis of the nanoparticle composite is discussed, and a mechanism tentatively proposed. In addition, the effects of pH and temperature on the amount and size of as-prepared titania/protamine nanoparticle composite were systematically investigated.

Organic-inorganic hybrid capsules, which typically possess a hollow lumen and a hybrid wall, have emerged as a novel and promising class of hybrid materials and have attracted enormous attention. In comparison to polymeric capsules or inorganic capsules, the hybrid capsules combine the intrinsic physical/chemical properties of the organic and inorganic moieties, acquire more degrees of freedom to manipulate multiple interactions, create hierarchical structures and integrate multiple functionalities. Thus, the hybrid capsules exhibit superior mechanical strength (vs. polymeric capsules) and diverse functionalities (vs. inorganic capsules), which may give new opportunities to produce high-performance materials. Much effort has been devoted to exploring innovative and effective methods for the synthesis of hybrid capsules that exhibit desirable performance in target applications. This tutorial review firstly presents a brief description of the capsular structure and hybrid materials in nature, then classifies the hybrid capsules into molecule-hybrid capsules and nano-hybrid capsules based upon the size of the organic and inorganic moieties in the capsule wall, followed by a detailed discussion of the design and synthesis of the hybrid capsules. For each kind of hybrid capsule, the state-of-the-art synthesis methods are described in detail and a critical comment is embedded. The applications of these hybrid capsules in biotechnological areas (biocatalysis, drug delivery, etc.) have also been summarized. Hopefully, this review will offer a perspective and guidelines for the future research and development of hybrid capsules.

Biosilica with a highly complex and intricate structure can be formed by a diatom under physiological conditions in the presence of silaffins. Herein, the biosilicification process in vivo is mimicked. A natural cationic polypeptide, protamine, was for the first time utilized in vitro to inspire and template silica formation at ambient temperature and neutral pH conditions. The silica-precipitating and templating effect of protamine was first tentatively elucidated. Then, this biomimetic silicification process was performed on the outer surface of liquid-core alginate (Alg) capsules in which β-glucuronidase (GUS) was preencapsulated. An alginate/protamine/silica (APSi) hybrid capsule with a distinct liquid core-solid shell structure was thus fabricated. The rigid, mesoporous silica shell dramatically inhibited the swelling of the capsule and effectively enhanced the mass transfer of substrates and products. Meanwhile, the biocompatible polysaccharide liquid core created a benign microenvironment and well preserved the three-dimensional structure of GUS. The stability of encapsulated GUS was significantly enhanced after silicification, and no loss in activity was found after 10 reaction cycles. Moreover, the relative activity of GUS encapsulated in APSi capsules reached 125%, not only exceeding that encapsulated in Alg capsules but also being higher than that of the free enzyme.

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