Silver cluster formation, dynamics, and chemistry in metal-organic frameworks.
Synthetic methods used to produce metal nanoparticles typically lead to a distribution of particle sizes. In addition, creation of the smallest clusters, with sizes of a few to tens of atoms, remains very challenging. Nanoporous metal-organic frameworks (MOFs) are a promising solution to these problems, since their long-range crystalline order creates completely uniform pore sizes with the potential for both steric and chemical stabilization. We report a systematic investigation of silver nanocluster formation within MOFs using three representative MOF templates. The as-synthesized clusters are spectroscopically consistent with dimensions < or =1 nm, with a significant fraction existing as Ag(3) clusters, as shown by electron paramagnetic resonance. Importantly, we show conclusively that very rapid TEM-induced MOF degradation leads to agglomeration and stable, easily imaged particles, explaining prior reports of particles larger than MOF pores. These results solve an important riddle concerning MOF-based templates and suggest that heterostructures composed of highly uniform arrays of nanoparticles within MOFs are feasible.
Houk
Ronald J T
RJ
Sandia National Laboratories, Livermore, California 94551-0969, USA.
Jacobs
Benjamin W
BW
El Gabaly
Farid
F
Chang
Noel N
NN
Talin
A Alec
AA
Graham
Dennis D
DD
House
Stephen D
SD
Robertson
Ian M
IM
Allendorf
Mark D
MD