Tuning Bismuth Metal-Organic Framework Topology for Enhanced Photocatalytic NO Oxidation.

Abstract

Precise topological-structural control over bismuth-based metal-organic frameworks (Bi-MOFs) is hampered by the challenge of balancing thermodynamics and kinetics. Such balance is achieved in three well-defined Bi-MOFs with crystalline, semi-crystalline, and amorphous topologies via a straightforward secondary building unit approach in bismuth-2-aminoterephthalic acid (Bi-BDC-NH2). The structure of Bi-BDC-NH2 is confirmed by single-crystal X-ray diffraction (XRD) to consist of BiO9 nodes. The amount of 2-aminoterephthalic acid is varied to modulate the topology via competitive complexation and thus control the thermodynamic and kinetic nucleation products. Through regulating the ligand-to-metal ratio of H2BDC-NH2 to Bi, an appropriate balance of the thermodynamic-versus-kinetic structural "trade-off" is achieved. The fine topologies of Bi-MOFs are determined by single-crystal XRD, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption fine structure. For the first time, it is reported that applying Bi-MOFs with varying topological structures as photocatalysts for removing nitric oxide (NO) demonstrates that the amorphisation improves the photogenerated charge separation efficiency and adsorption and activation of O2. This work offers a guide in complex topological-structural control, which is conducive for those to develop highly efficient MOFs-based photocatalysts.