LAUSR

Molecular sieves are crystalline materials with ordered pores of molecular sizes. Zeolites and metalorganic frameworks (MOFs) are the most utilized molecular sieve materials. Zeolites are silicon dioxide with ordered micropores (0.5 nm – 2 nm), some of which have silicon substituted with metal atoms for added functionality. [1] MOFs are 3-D coordination networks composed of metal nodes and linkers, where the linkers create a 3-D scaffold that lead to ordered porosity. [2] These molecular cavities give molecular sieves the capability to recognize and manipulate molecules at microscale. For example, zeolite ZSM-5 is an important catalyst that can produce gasoline by catalytic cracking of heavy hydrocarbons, due to its special pore size and pore connections in the crystal structure. ZIF-8 and related materials are MOFs that can be used for CO2/CH4 separation, due to its chemical composition that results in selective adsorption and accelerated transport of CO2 in its molecular cavities. In addition to the crystal structure that decides pore size and topology, the morphology of the crystals is also of great importance. For example, 2-D molecular sieve particles are beneficial for gas separation due to the shortened diffusion path that leads to higher gas permeance; catalyst nanoparticles with sub-100 nm size are beneficial for fully exploiting the reactive surface area of nanoparticles for catalytic reactions.