The one-step conversion of cellulose to C6-alcs. via green and energy efficient approaches has, as far as we are aware, not been reported. Such a process presents a considerable challenge, the two key problems being (1) finding a suitable solvent that dissolves the cellulose, and (2) the development of advanced catalytic chem. for selective cleavage of the C-O-C bonds (glycosidic bonds) connecting glucose residues. The dissoln. of cellulose has been recently realized by using ionic liqs. as green solvents; there is still no efficient method, such as selective hydrogenation, for the precise C-O-C cleavage under mild conditions, however. Cellobiose is a glucose dimer connected by a glycosidic bond and represents the simplest model mol. for cellulose. We disclose in this communication that the one-step conversion of cellobiose to C6-alcs. can be realized by selectively breaking the C-O-C bonds via selective hydrogenation using a water-sol. ruthenium nanocluster catalyst under 40 bar H2 pressure.