Toward this end, the immobilization of homogenous catalysts onto amorphous crosslinked polymers is a common strategy that benefits from the compositional diversity, synthetic flexibility, and tunable physical properties of polymers, (Fig. ). When such catalyst-functionalized polymer networks are in a swollen state (i.e., gels), reagent mobility can approach that within solution, facilitating reasonable reaction rates. Nevertheless, the amorphous nature of such materials makes it nearly impossible to control the local catalyst environment, giving rise to unpredictable outcomes and potential batch-to-batch variation. Crystalline polymer networks, including coordination polymers such as metal organic frameworks (MOFs), can overcome this challenge by enabling exquisite local tuning of catalyst environments; however, such materials are often glassy and brittle, they may require harsh and extended annealing conditions for their formation, and they can suffer reagent flux issues to and from their crystalline pores, leading to lowered catalytic efficiency compared to homogeneous processes. An ideal heterogeneous catalysis platform would ( Here, we demonstrate proof-of-concept of such a system. Our approach leverages metal-organic cage/polyhedra (MOC)-crosslinked polymer gels, where the MOCs serve as nanoscale porous junctions that provide tunable and predictable local catalyst environments; the polymer strands that link MOCs control the physical and mechanical properties of the materials (Fig. ). These "polyCATs" are readily prepared from simple mixing of 3-4 components, depending on the need: (i) endohedral catalystfunctionalized ligands (CLs), (ii) exohedral polymer-functionalized ligands (PLs), (iii) spacer ligands (SLs) where necessary to accommodate larger catalysts, and (iv) metal ions (e.g., Pd(II)), offering a "plugand-play" approach to heterogenous catalysis, as demonstrated through the realization of two mechanistically distinct traditionally homogeneous catalytic transformations (a TEMPO-catalyzed oxidation and a Au(I)-mediated cyclization), facile catalyst recycling and correspondingly improved catalyst turnover numbers (TONs), and, in one case, catalyst reactivity that is impossible for the analogous homogeneous system.