Macroporous

Macroporous refers to materials whose pore diameters exceed approximately 50 nanometers, placing them in the macroporous category of the IUPAC framework for porous materials (microporous <2 nm, mesoporous 2–50 nm, macroporous >50 nm). Macropores enable rapid transport of fluids and macromolecules through large channels and an interconnected network, which is advantageous for applications requiring fast diffusion.

The pore structure is described by pore size distribution, total pore volume, and connectivity. Macroporous materials often have moderate to high porosity with accessible surfaces that allow convective transport, though surface area may be lower than in microporous or mesoporous materials.

Common preparation methods include hard templating, using sacrificial spheres or networks to create uniform macropores; soft templating with surface-active agents; phase separation and porogen leaching; gas foaming; freeze casting and freeze-drying; and self-assembly approaches. Post-synthesis treatments such as sintering or carbonization tailor mechanical properties.

Macroporous materials span ceramics (such as alumina and silica networks), polymers (including polyurethane and poly(methyl methacrylate) foams), carbon materials (macroporous carbons from templated precursors), and metal foams with open-cell structures. The choice of material and templating route determines pore size, connectivity, and mechanical stability.

Applications are broad: catalyst supports and reactors with improved mass transport; adsorption and separation of large molecules; enzyme immobilization and bioreactors; tissue engineering scaffolds; filtration membranes; and energy storage or electrochemical devices where rapid ion transport is beneficial.

Characterization methods include mercury intrusion porosimetry for macropore distribution, micro-computed tomography for 3D structure, and imaging techniques; BET surface area measurements are less informative for predominantly macroporous systems.