Immobilization of lysozyme proteins on a hierarchical zeolitic imidazolate framework (ZIF-8).

A hierarchical zeolitic imidazolate framework-8 (micro/meso-ZIF-8) was fabricated by using cetyltrimethylammonium bromide as a structure-controlling agent and l-histidine as co-templates. Compared to the conventional microporous ZIF-8 (micro-ZIF-8), the hierarchical porous structure of micro/meso-ZIF-8 contains micropores and maximum mesopores of around 35.6 nm. The as-prepared hierarchical micro/meso-ZIF-8 featured a large surface area and superior spontaneous adsorption activity than micro-ZIF-8 towards lysozyme (LZM), bovine hemoglobin (BHb) and bovine serum albumin (BSA), and the adsorption capacity increased with the decreasing of the protein size due to the molecule cutoff effects. The maximum adsorption capacity of LZM on micro/meso-ZIF-8 was higher than most of the reported results under similar adsorption conditions. The analyses of adsorption kinetics and thermodynamics implied that the adsorption mechanism mainly involved physical adsorption. Moreover, the micro/meso-ZIF-8 showed good thermal stability against temperature and excellent regeneration ability in the recycling adsorption experiments. This work proposed herein opens a broad application prospect of hierarchical MOFs in biological molecule separation, immobilization and enrichment.