Confined channels and cages of zeolites have been widely used as shape-selective heterogeneous catalysts in the (petro)chemical industry. A common objective in the design of zeolite is to overcome the inherent mass transport limitations of micropores. The advent of two-dimensional1 or self-pillared zeolites2 exhibit superior catalytic performance to conventional zeolites. In this talk, we will describe an alternative approach to reduce the internal diffusion limitations of zeolites via the introduction of fin-like protrusions on zeolite surfaces by secondary growth. We will discuss the synthesis of multiple frameworks with nano-sized fins (size a) which exhibit an identical crystallographic registry with the interior crystal (size b) and show their superior catalytic performance relative to conventional analogues.
This new class of mass transport enhanced zeolites were synthesized using secondary growth mixtures prepared with a finely tuned composition that allows for the epitaxial growth of fins on the surface of seed crystals. Here we will discuss examples of several finned zeolites with disparate 3-dimensional pore networks to demonstrate the broader applicability of this approach. We also demonstrate a proof of concept using commercial zeolite samples where finned analogues improve their catalytic performance. Our studies of synthesis and MTH catalytic testing as benchmark reaction are coupled with state-of-the-art characterization using techniques such as high-resolution electron tomography, operando spectroscopy, novel acid titration methods, and molecular modeling to correlate structural features of finned zeolites and their diffusion properties with enhanced catalyst performance.
