Covalent Organic Framework Cladding on Peptide-Amphiphile-Based Biomimetic Catalysts

Abstract

Peptide-based biomimetic catalysts are promising materials for efficient catalytic activity in various biochemical transformations. However, their lack of operational stability and fragile nature in non-aqueous media limit their practical applications. In this study, we have developed a cladding technique to stabilize biomimetic catalysts within porous covalent organic framework (COF) scaffolds. This methodology allows for the homogeneous distribution of peptide nanotubes inside the COF (TpAzo and TpDPP) backbone, creating strong noncovalent interactions that prevent leaching. We synthesized two different peptide-amphiphiles, C10FFVK and C10FFVR, with lysine (K) and arginine (R) at the C-termini, respectively, which formed nanotubular morphologies. The C10FFVK peptide-amphiphile nanotubes exhibit enzyme-like behavior and efficiently catalyze C–C bond cleavage in a buffer medium (pH 7.5). We produced nanotubular structures of TpAzo–C10FFVK and TpDPP–C10FFVK through COF cladding by using interfacial crystallization (IC). The peptide nanotubes encased in the COF catalyze C–C bond cleavage in a buffer medium as well as in different organic solvents (such as acetonitrile, acetone, and dichloromethane). The TpAzo–C10FFVK catalyst, being heterogeneous, is easily recoverable, enabling the reaction to be performed for multiple cycles. Additionally, the synthesis of TpAzo–C10FFVK thin films facilitates catalysis in flow. As control, we synthesized another peptide-amphiphile, C10FFVR, which also forms tubular assemblies. By depositing TpAzo COF crystallites on C10FFVR nanotubes through IC, we produced TpAzo–C10FFVR nanotubular structures that expectedly did not show catalysis, suggesting the critical role of the lysines in the TpAzo–C10FFVK.

Improving the Bioactivity and Stability of Embedded Enzymes by Covalent Organic Frameworks

“…Immobilizing enzymes on solid supports is an effective strategy to enhance their stability, reusability, and easy operation, which are desired for the development of enzyme catalysts. − Due to the advantages of reticular chemistry materials (such as high porosity, stability, and tunability), metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) have recently been regarded as excellent supports for enzyme immobilization. − To date, a series of MOFs, especially ZIFs, have been widely explored for de novo immobilizing enzymes; however, the bioactivity of immobilized enzymes is sometimes far from satisfactory, which is caused by the diffusion barriers of ZIFs (pore size of the commonly used ZIF-8: 0.34 nm) and the unavoidable activity loss during the immobilizing process, such as harmful metal ions. − Meanwhile, a lot of research has successfully enhanced the activity of the immobilized enzyme, such as modulating the microenvironment, shortening diffusion paths, and enabling biocatalytic cascades. − However, there is still an essential problem that has not been solved in enzyme@MOF biocomposites, which is the unavoidable influence of metal ions on enzymatic activity. Some reports have proved that metal ions can coordinate with enzymes, which may perturb their conformation or cover their active sites, leading to unpredictable changes in activity and even the complete inactivation of enzymes. − …”

Novel Capturer-Catalyst Microreactor System with a Polypyrrole/Metal Nanoparticle Composite Incorporated in the Porous Honeycomb-Patterned Film

“…4 However, the endeavor of choosing the right template is critical, and it can be challenging to find suitable templates for some desired structures. 5 Moreover, it is difficult to remove the template without damaging the final structure, and traces of residue may remain, affecting the final material's properties. 2 In this context, breath figure (BF) methods have emerged as a promising technique for the fabrication of highly ordered, porous films similar to the honeycomb structure pattern (HCP) first reported by Widawski et al 6 The formation of the porous films by the BF method was facilitated by casting the polymer solution under humidity.…”

“…Self-templated synthesis allows precise control over the final product’s size, shape, and morphology and a high degree of pore uniformity . However, the endeavor of choosing the right template is critical, and it can be challenging to find suitable templates for some desired structures . Moreover, it is difficult to remove the template without damaging the final structure, and traces of residue may remain, affecting the final material’s properties …”

Assessing CO2 Adsorption Behavior onto Free-Standing, Flexible Organic Framework-PVDF Composite Membrane: An Empirical Modeling and Validation of an Experimental Data Set

“…Countless attempts have been made in recent years to engineer polymeric or derived polymeric composite materials that possess excellent CO 2 adsorption attributes. In this regard, there is a rising interest in exploring the avenues of polymer-COF membranes, since COFs, due to their astounding property of organic coordination framework, offer enhanced processability and compatibility to be employed as membrane materials with varied polymers. − COF-membranes have been assessed for their usefulness in energy storage, water purification, biofuel generation, and other fields, − and it is projected that the field of membrane technology will increase in the next years. Many techniques for fabricating COF membranes have been investigated, including solvothermal, interfacial polymerization, layer-by-layer stacking, and so on, − but the demand for simple and active production methods is still unmet.…”