Pyrolysis regulation of ZIF-8 to construct a robust multifunctional N-doped macroporous carbon for lipase immobilization

Abstract

Pyrolyzing ZIF-8 into N-doped carbon is now inspiring new potential of ZIF-8 for extensive applications. However, the exploration of such ZIF-8-derived carbon for biotechnological applications has been rarely investigated, especially in this context that imidazole derivatives are of rich functionality in life science. Herein, we reported a facile temperature-dependent pyrolysis method to achieve the effective N-doping in ZIF-8-derived macroporous carbon, which was systematically investigated for the immobilization of lipase from Thermomyces lanuginosus (TLL) in biodiesel production. MNC-600 (macroporous N-doped carbon derived at 600 °C) exhibited the best immobilization performance, with the highest specific activity of 190.6 U mg−1, a 36.9% increase than free TLL. Moreover, MNC-600@TLL showed superior effectiveness and robustness in biodiesel production. A much faster rate of conversion and the highest biodiesel yield of 87.4% were observed. After eight successive batches of recycling, MNC-600@TLL retained 93.4% of its initial activity. XPS analysis revealed the evolution of N species during the pyrolysis of ZIF-8. It was proposed that the abundant doping of pyrrolic N species played a major role in the surprising performance of MNC-600, mainly through hydrogen bonding interactions, which simultaneously realized the activation of reactants as well as the in-situ hydrophobization of biocatalyst. This report is anticipated to pave a way for the exploration of ZIF-8-derived N-doped carbon for extensive biotechnological applications.