Single-crystalline Zn2GeO4 nanobelts with lengths of hundreds of micrometers, thicknesses as small as similar to 7 nm, and aspect ratios of up to 10 000 were synthesized in a binary ethylenediamine/water solvent system using a solvothermal route. The ultralong and ultrathin geometry of the Zn2GeO4 nanoribbon proves to greatly promote the photocatalytic activity toward reduction of CO2 into renewable hydrocarbon fuel (CH4) in the presence of water vapor.