Zeolite confined rhodium(0) nanoclusters as highly active, reusable, and long-lived catalyst in the methanolysis of ammonia-borane

Abstract

Addressed herein is the preparation, characterization and the catalytic use of zeolite confined rhodium(0) nanoclusters in the methanolysis of ammonia-borane. Rhodium(0) nanoclusters could be generated in zeolite-Y by a two-step procedure: (i) incorporation of rhodium(III) cations into the zeolite-Y by ion-exchange and (ii) reduction of rhodium(III) ions within the zeolite cages by sodium borohydride in aqueous solution, followed by filtration and dehydration by heating to 550°C under 10−4Torr. Zeolite confined rhodium(0) nanoclusters are stable enough to be isolated as solid materials and characterized by ICP-OES, XRD, SEM, EDX, HR-TEM, XPS and N2 adsorption–desorption technique. The zeolite confined rhodium(0) nanoclusters are isolable, bottleable, redispersible and reusable as an active catalyst in the methanolysis of ammonia-borane even at low temperatures. They provide exceptional catalytic activity with an average value of TOF=380h−1 and unprecedented lifetime with 74,300 turnovers in the methanolysis of ammonia-borane at 25±0.1°C. The work reported here also includes the full experimental details of the collection of a wealth of previously unavailable kinetic data to determine the rate law, and activation parameters (Ea, ΔH≠ and ΔS≠) for the catalytic methanolysis of ammonia-borane.