Three-Dimensional Visualization of Defects Formed during the Synthesis of Metal-Organic Frameworks: A Fluorescence Microscopy Study

摘要

Porous crystalline frameworks are highly ordered solids in which all pores have exactly the same size and shape, as determined by the crystal structure, that is, the lattice parameters, symmetry, and coordinates of the atoms. This regular spacing of uniform nanometer-sized pores lays the foundation for the use of these materials in applications involving shape- and size-selective adsorption, catalysis, and sensing.When the regular porous interior of such solids is disrupted by the introduction of defects, the behavior with respect to the intended application can be drastically altered. Imperfections of the crystal lattice do not, however, necessarily lead to a deterioration of the material's performance. In fact, controlled introduction of defects is standard practice for some applications of porous materials. A well-known example is ultrastable Y zeolite (USY), a key cracking catalyst used for upgrading high-boiling fractions of petroleum crude, which is prepared by partial destruction of the parent zeolite Y framework. This treatment is used to control the framework composition and introduce meso-porosity in order to maximize catalyst productivity and lifetime.