Hyperfine adjustment of flexible pore-surface pockets enables smart recognition of gas size and quadrupole moment.

The pore size and framework flexibility of hosts are of vital importance for molecular recognition and related applications, but accurate control of these parameters is very challenging. We use the slight difference of metal ion size to achieve continuous hundredth-nanometer pore-size adjustments and drastic flexibility modulations in an ultramicroporous metal-organic framework, giving controllable N adsorption isotherm steps, unprecedented/reversed loading-dependence of H adsorption enthalpy, quadrupole-moment sieving of CH/CO, and an exceptionally high working capacity for CH storage under practical conditions (98 times that of an empty cylinder). single-crystal X-ray diffraction measurements and multilevel computational simulations revealed the importance of pore-surface pockets, which utilize their size and electrostatic potential to smartly recognize the molecular sizes and quadruple moments of gas molecules to control their accessibility to the strongest adsorption sites.