A search for diphoton events with large missing transverse energy is presented. The data were collected with the ATLAS detector in proton-proton collisions at $\sqrt{s}=7\text{ }\text{ }\mathrm{TeV}$ at the CERN Large Hadron Collider and correspond to an integrated luminosity of $3.1\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$. No excess of such events is observed above the standard model background prediction. In the context of a specific model with one universal extra dimension with compactification radius $R$ and gravity-induced decays, values of $1/R<729\text{ }\text{ }\mathrm{GeV}$ are excluded at 95% C. L., providing the most sensitive limit on this model to date.