NOVELTY - Making a zinc oxide structure, involves: a) preparing a mixture of i) zinc salt or hydrated or zinc oxalate, ii) first additive, iii) second additive selected from urea, urea derivative, thiourea, or thiorurea derivative, and iv) 1-3C aliphatic alcohol solvent; b) heating mixture of step a) to first temperature from 180-200 degrees C and maintaining mixture at first temperature for 1-12 hours; c) heating mixture of step b) to second temperature from 240-300 degrees C and maintaining mixture at second temperature for 1-12 hours; d) removing alcohol solvent; and e) calcining mixture of step d) in air.    USE - For making a zinc oxide structure (claimed) used as a catalyst for methanol decomposition and formation at low temperature, dimethyl carbonate formation and photocatalysis; in solar cells, fuel cells, electrochemical cells, direct methanol fuel cells (DMFC), electric vehicle propulsion, and in alternative energy technologies, such as hydrogen generation or storage; and also in high density magnetic data storage and as a component or interconnect in nanodevices.    ADVANTAGE - The method is simple, low-cost and practical; and is easy to scale up. The ZnO structures and structure assemblies are formed via a template-free, halide-free, efficient wet chemical method. The method uses a one-pot approach using the inexpensive precursor zinc nitrate, optionally containing water, as a starting material. The methods employ ZnO structures and structure assemblies which are capable of catalyzing hydrogenation of carbon dioxide.    DETAILED DESCRIPTION - Making a zinc oxide structure, involves: a) preparing a mixture of i) a zinc salt or a hydrated or zinc oxalate, ii) a first additive, the first additive is an alcohol comprising a phenyl group, iii) a second additive selected from urea, urea derivative, thiourea, or thiorurea derivative, and iv) an 1-3C aliphatic alcohol solvent; b) heating the mixture of step a) to a first temperature from 180-200 degrees C and maintaining the mixture at the first temperature for 1-12 hours; c) heating the mixture of step b) to a second temperature from 240-300 degrees C and maintaining the mixture at the second temperature for 1-12 hours; d) removing the alcohol solvent from the mixture of step c); and e) calcining the mixture of step d) in air.