AbstractHighly porous and hyper‐cross‐linked polymers (HCPs) have a range of applications and are typically synthesized in an unsustainable manner. Herein, HCPs were synthesized from abundant biobased or biorelated compounds in sulfolane with iron(III) chloride as Lewis acid catalyst. As reactants, quercetin, tannic acid, phenol, 1,4‐dimethoxybenzene, glucose, and a commercial bark extract were used. The HCPs had high CO2 uptake (up to 3.94 mmol g−1 at 0 °C and 1 bar), total pore volumes (up to 1.86 cm3 g−1), and specific surface areas (up to 1440 m2 g−1). 1H NMR, 13C NMR, and IR spectroscopy, wide‐angle X‐ray scattering, elemental analysis, and SEM revealed, for example, that the HCPs consisted of amorphous and cross‐linked aromatic and phenolic structures with significant contents of aliphatics, oxygen, and sulfur.