Tailored Design of Mesoporous Metal Organic Framework Single Crystals by Kinetics-Mediated Micelle Assembly for Efficient Asymmetrical Single-Atom Catalysis.

Abstract

Constructing mesoporous metal organic frameworks (MesoMOFs) with customizable meso- and micro-environment is pivotal for asymmetric single-atom catalysis, yet it is impeded by the strong self-growth tendency of MOFs. In this work, a novel kinetics-mediated micelle assembly strategy is introduced to realize the general fabrication of mesoporous zeolitic imidazolate framework (ZIF) single crystals. Spectroscopic characterizations and cryo-electron cryomicroscopy reveal that the strategic use of water accelerates the MOFs kinetics-mediated micelle assembly via enhancing ligand deprotonation, which suppresses the MOFs self-growth, facilitating the cooperative assembly of micelles and MOFs. Furthermore, the water amount can modulate the Flory-Huggins interaction parameters between the solvents and micelles, thereby precisely controlling the pore architectures from spherical, cylindrical to vesicular. Such versatile synthesis creates a new class of mesoporous asymmetric CoN₃O single-atom catalyst. Synchrotron spectral characterizations and theoretical calculations uncover that this asymmetric geometry localizes more electrons around Co center and upshift the d-band center, stabilizing O* intermediates and promoting the oxygen reduction reaction (ORR). Consequently, the asymmetric mesoporous catalyst exhibits a half-wave potential (0.91 V in alkaline media) and a high power density (185 mW cm^-2) in a zinc-air battery. This work provides a new approach for designing MesoMOFs for asymmetric single-atom catalysis.