Capitalizing on the concept that everything proceeds faster with a little cooperation, researchers showed how designing cooperation into solid catalysts leads to enormous benefits.Catalysts attached to a porous solid support are preferred industrially because they are easier to separate from liquid products and reuse. But, these bound catalysts typically do not perform as well and probing their interiors to figure out how to improve them has proved difficult until now. Using new solid-state nuclear magnetic resonance (SSNMR) methods (the equivalent of running an MRI on the catalyst) and innovative synthetic strategies, researchers showed how to probe their inner workings and make optimization possible. Scientists demonstrated this approach on a carbon-carbon bond forming reaction routinely used in chemical manufacturing and biofuel production. Two key insights were revealed. First, access into and out of the pores is blocked by a chemical intermediate. Making the pores a mere 0.8 nanometers wider increased the catalytic activity 20-fold! Knowing the structure of the intermediate, researchers were able to modify the catalyst to eliminate the bottleneck without making the pore wider. This heterogeneous catalyst is significantly more active than the homogeneous catalysts, contrary to expectations. Why? SSNMR showed the support brings the reactants and catalytic groups together, resulting in the enhanced, cooperative activity not possible with the untethered catalyst. This work sets the stage for significant innovations for commonly used catalytic processes.
Substrate Inhibition in the Heterogeneous Catalyzed Aldol Condensation: A Mechanistic Study of Supported Organocatalysts