<p>Anchoring a molecular metal complex on a solid support is becoming the most fascinating field of catalysis, as it bridges homogeneous and heterogeneous catalysis. However, owing to the spatial confinement of surface chemistry in supported catalysts, they display an inevitable loss of activity and selectivity compared to the homogeneous counterparts. Here, we propose a strategy to construct swellable supported catalysts where active metal centers are located on a swellable support for enhanced performance, where the occurrence of spontaneous swelling in the reaction medium facilitates active site exposure and reactant diffusion. The key to the strategy involves simultaneous immobilization of Al-porphyrins and quaternary ammonium salts on swellable Merrifield resin, forming swellable bifunctional supported catalysts (SBSCs), which were characterized in the swollen state by polarization microscopy and X-ray photoelectron spectroscopy. Surprisingly, SBSCs displayed a record-high activity of 2540 g g⁻¹ h⁻¹ for the cycloaddition of CO₂/propylene oxide even under low catalyst loading (1.28 × 10⁻³ mol%, based on Al), significantly outperforming the non-swellable counterpart (~0 g g⁻¹ h⁻¹). Moreover, because of the heterogeneous attribute, the repeatable synthesis of colorless cyclic carbonate was realized for over 6 cycles without significant loss of activity. An in-depth understanding of reaction kinetics and mechanisms in SBSCs can be rationally analyzed owing to the high accessibility of active sites. This swellable-supported catalyst strategy is expected to pave the way for the design of next-generation heterogeneous catalysts.</p>