An increased demand for more sustainable approaches in the chemical industry is being driven by considerable socio-economic and environmental changes. As a result, reusable, energy efficient, and selective catalysts have become a key pillar in the principles of green chemistry. By the immobilisation of homogeneous catalysts or equivalent chemical functionality onto inert insoluble frameworks, effective heterogeneous catalysts that adhere to these principles can be realised. Heterogeneous catalysts offer advantages over homogeneous equivalents, such as use in continuous flow processes, simple separation and recovery from reactants and products, and straightforward recycling. However, reduced catalytic activity, high-costs, and poor stabilities can often hold-back the application of such catalysts in industry. Immobilisation requires the synthesis of pre-functionalised frameworks, followed by the anchoring of active sites, often requiring multistep procedures and expensive reagents. Moreover, immobilisation can alter the microenvironment of active sites, leading to decreased activity or accessibility for reactants. To make heterogeneous catalysts competitive with homogeneous equivalents, their active sites need to be dense and accessible, their production should exploit low-cost design, and their implementation has to offer simple operation and compatibility with many facets of modern catalysis.