Catalysis

Structural rigidity

Chemical physics

Materials science

Molecular sieve

Biochemistry

Molecule

Silicon

Rigidity (electromagnetism)

Organic chemistry

Mathematics

Zeolite

Molecular dynamics

Computational chemistry

Geometry

Composite material

Tetrahedron

Combinatorics

Crystallography

Chemistry

Topology (electrical circuits)

Optoelectronics

Benzene

Science

The crystallographic pore sizes of zeolites are substantially smaller than those inferred from catalytic transformation and molecular sieving capabilities, which reflects flexible variation in zeolite opening pores. Using in situ electron microscopy, we imaged the straight channels of ZSM-5 zeolite with benzene as a probe molecule and observed subcell flexibility of the framework. The opening pores stretched along the longest direction of confined benzene molecules with a maximum aspect change of 15%, and the Pnma space group symmetry of the MFI framework caused adjacent channels to deform. This compensation maintained the stability and rigidity of the overall unit cell within 0.5% deformation. The subcell flexibility originates mainly from the topologically soft silicon-oxygen-silicon hinges between rigid tetrahedral SiO4 units, with inner angles varying from 135° to 153°, as confirmed by ab initio molecular dynamics simulations.

In situ imaging of the sorption-induced subcell topological flexibility of a rigid zeolite framework