A novel type of energy donor-acceptor system on a clay surface has been prepared. The energy transfer between an energy-donating cationic pyrene derivative (An-Py) and an energy-accepting tris(bipyridine)ruthenium complex (Ru) on the clay surface was investigated using absorption, emission, and lifetime measurements. An obvious energy transfer was observed, and one Ru molecule quenched the emission from five molecules of An-Py with an emission quenching efficiency of 85% on the clay surface. This suggests that the light energies absorbed by five of the An-Py molecules were accumulated in the one Ru molecule. Near-quantitative emission quenching was observed for stoichiometric amounts of An-Py and Ru. The apparent quenching rate constant is approximately 10 L mol s, and thus the quenching rate constant is 10-10 times higher than the diffusion rate constant in a homogeneous solution.