Disentangling protein confinement from surface adsorption in hierarchical zirconium metal-organic frameworks

A persistent challenge in protein immobilization within metal-organic frameworks (MOFs) is distinguishing genuine internal confinement from surface adsorption and interparticle voids, which can mimic encapsulation despite fundamentally different spatial microenvironments. Incorporating mesochannels to produce hierarchical UiO-66-NH 2 and MOF-808 nanoparticles, prepared by micelle templating, offers a strategy to overcome this ambiguity while preserving their intrinsic microporosity. Evidence from pore accessibility, pulsed field gradient NMR, and small-angle X-ray scattering is consistent with protein association within mesochannel environments. In the hierarchical hosts, loaded bovine serum albumin shows enhanced resilience to thermal stress. Together, these results are consistent with internal mesochannel confinement contributing to protein stabilization while preserving molecular accessibility in MOFs. Extending confinement to function, Candida antarctica lipase B immobilized in these hosts remains catalytically active at elevated temperature. In contrast to a commercial immobilized preparation, it retains a larger fraction of its activity in the first reuse cycles.