Development of three-dimensional, four-connected framework structures with extra-large open pores

Two series of hypothetical zeolite frameworks with extra-large open pores are constructed based on five-membered ring secondary building units (SBUs) with the 'combination SBU-SG approach' - i.e., constructing a net based on the space group (SG) of a selected building unit. Optimization of the initial coordinates of atoms of these structures is achieved by Monte Carlo methods using simulated annealing, based on a consistent molecular mechanics force field. The heats of formation and theoretical X-ray powder diffraction patterns of these novel structures are calculated. The relative stability of these structures is analyzed and compared with that of the zeolite mordenite. The effect of SBUs on the stability of the framework is discussed.