intrapore

Intrapore refers to phenomena and processes that occur within the interior of the pores of a solid material. The term is commonly used in chemistry, materials science, catalysis, environmental engineering, and energy storage to distinguish what happens inside pores from external or interparticle transport. Porous materials such as zeolites, activated carbon, silica, and metal‑organic frameworks frequently exhibit intrapore transport that governs overall performance in adsorption, catalysis, and separations.

Intrapore diffusion and transport describe how molecules and ions move inside pore networks. Diffusion can be hindered by confinement, pore geometry, surface interactions, and adsorption to pore walls, leading to an effective diffusion coefficient that is typically smaller than the bulk value. In very small pores, transport may follow Knudsen diffusion, single‑file diffusion, or a combination of molecular and surface diffusion. Diffusion behavior varies with pore size: micropores (less than 2 nm) often show strong confinement and adsorption effects; mesopores (2–50 nm) exhibit a mix of molecular and surface diffusion; macropores (greater than ~50 nm) approach bulk diffusion behavior.

Measurement and modeling approaches include pulsed‑field‑gradient NMR, tracer experiments, and uptake or breakthrough tests to estimate intrapore diffusion coefficients. Models often treat D_eff as a function of porosity, tortuosity, pore size distribution, and surface interactions, incorporating hindered diffusion and, when relevant, surface diffusion mechanisms.

Applications and implications cover catalyst design, where intrapore transport limits reaction rates and selectivity; gas and liquid separations in porous adsorbents; energy storage in porous electrodes where ion diffusion within pores affects capacity and power; and environmental remediation, where intrapore diffusion influences contaminant transport in soils and mineral matrices.

See also porosity, adsorption, diffusion, zeolites, MOFs, activated carbon.