Bioactive Covalent Organic Framework Capsules for Lactate Synthesis

A bioactive covalent organic framework(bio-COF) capsuleis fabricated through enzyme-induced growth and crystallization ofCOFs on a sacrificial template for sustainable lactate synthesis. Capsular covalent organic frameworks (COFs) offer uniqueand highlytunable spaces for enzyme immobilization. Herein, a kind of bioactivecovalent organic framework (bio-COF) capsule was fabricated througha sacrificial templating method for the synthesis of lactate frompyruvate. The synthesis time of COF and the amount of enzyme wereoptimized during the preparation of bio-COF capsules. The enzymeswere entrapped in the capsule wall with a thickness of similar to 240nm and a major pore size of similar to 1.8 nm. The porous structure ofbio-COF capsules ensured rapid diffusion of substrates through thecapsule wall. Thereby, the bio-COF capsule retained 70% of its initialactivity under reaction conditions at pH 6 and 35 degrees C. The confinementof the capsule wall toward enzymes remarkably improved the operationalstability and organic solvent tolerance. After treatment under pH4 and 60 degrees C for 120 min, the bio-COF capsules still retainedthe relative activities of 79 and 60%, respectively. Furthermore,the bio-COF capsules exhibited superior recyclability, retaining over85% relative activity after 8 cycles. Our study offers a general platformfor immobilizing enzymes and expands the potential application ofCOFs in the green biomanufacturing field.