Controllable Synthesis of Hollow Microtubular Covalent Organic Frameworks as an Enzyme-Immobilized Platform for Enhancing Catalytic Activity

Despite great achievement that has been made in the synthesis of covalent organic frameworks (COFs), precise construction of COFs with well-defined nano/microstructures poses a rigorous challenge. Herein, we introduce a simple template-free strategy for controllable synthesis of hollow microtubular COFs. The obtained COFs show a spontaneous morphology transformation from a microfiber to a hollow microtubular structure when the concentrations of catalytic acid are regulated elaborately. Furthermore, the as-prepared COFs exhibit high crystallinity, well-defined hollow tubular morphology, and high surface areas (∼2600 m2/g). Taking the advantages of the unique morphological structure, the hollow microtubular COFs can serve as an ideal host material for enzymes. The resultant biocomposites show high catalytic performance and can be successfully applied to rapid and high-efficiency proteolysis of proteins. This work blazes a trail for controllable synthesis of the hollow microtubular COFs through a template-free process and expands the application of COFs as a promising platform for enzyme immobilization.