The possibilities for porous materials are vast: hydrogen storage, mixed gas separations, to catalytic applications and more. We have designed apparatus for qualitative in-situ gas dosing for synchrotron X-ray and neutron powder diffraction applications. The result is that accurate dosing can be made per quantity of interest (moles of cations, per unit cell, per pore, etc.) and reactions can be followed with X-ray measurements. Neutron and X-ray powder results for gas separations in zeolites, metal-organic frameworks (MOFs) and porous carbons will be shown.