Heterogeneous catalysis of di-n-octyl phthalate by pepsin based on an ionic coordination regulation strategy driving the evolution of MOF pore structure

Metal-organic framework (MOF)-based immobilized enzymes with green catalytic and reusable features have been widely used in various fields. The pore structure modulation of MOF is the key to the application of MOF materials. The traditional MOF is only microporous, which affects the immobilization rate and catalytic activity of the enzyme. Here, ions that can interact with MOF coordination groups are used to induce the lattice structure of MOF to expand, forming porous carriers with high activity, which not only provides a stable microenvironment for pepsin, but also enables heterogeneous catalysis of pepsin. Pepsin was immobilized onto MOF carriers to form heterogeneous pepsin using immobilized enzyme technology, and the results showed that the immobilization rate of pepsin on MOF carriers modified with pore structure was increased from 49.25 % to 84.68 %. The prepared heterogeneous pepsin showed excellent removal performance of microplastic additive di-n-octyl phthalate (DNOP) contaminant with a removal rate of 95.68 % in 180 min, which is a completely innovative method for the removal of DNOP. In addition, the molecular models of heterogeneous pepsin and DNOP were established, the theoretical results were in agreement with the experimental results, and the degradation pathway of DNOP was analyzed by gas chromatography-mass spectrometry (GC–MS) technique. Our results demonstrate the potential of heterogeneous pepsin as a green catalyst, which can provide new ideas for the construction of heterogeneous enzyme catalysts and the removal of organic pollutants in the future.