When High‐Temperature Cesium Chemistry Meets Self‐Templating: Metal Acetates as Building Blocks of Unusual Highly Porous Carbons <jats:title>Abstract</jats:title><jats:p>Self‐templating is a facile strategy for synthesizing porous carbons by direct pyrolysis of organic metal salts. However, the method typically suffers from low yields (&lt;4%) and limited specific surface areas (SSA&lt;2000 m<jats:sup>2</jats:sup> g<jats:sup>−1</jats:sup>) originating from low activity of metal cations (e.g., K<jats:sup>+</jats:sup> or Na<jats:sup>+</jats:sup>) in promoting construction and activation of carbon frameworks. Here we use cesium acetate as the only precursor of oxo‐carbons with large SSA of the order of 3000 m<jats:sup>2</jats:sup> g<jats:sup>−1</jats:sup>, pore volume approaching 2 cm<jats:sup>3</jats:sup> g<jats:sup>−1</jats:sup>, tunable oxygen contents, and yields of up to 15 %. We unravel the role of Cs<jats:sup>+</jats:sup> as an efficient promoter of framework formation, templating and etching agent, while acetates act as carbon/oxygen sources of carbonaceous frameworks. The oxo‐carbons show record‐high CO<jats:sub>2</jats:sub> uptake of 8.71 mmol g<jats:sup>−1</jats:sup> and an ultimate specific capacitance of 313 F g<jats:sup>−1</jats:sup> in the supercapacitor. This study helps to understand and rationally tailor the materials design by a still rare organic solid‐state chemistry.</jats:p> 62 26 Wiley