See what you will probably never see in reality, thanks to the PCOD...

Three-dimensional SiO2 models (not DFT-optimized) with lowest framework density (FD) as predicted by GRINSP

Models extracted from the PCOD 2009 update

(Selected among 11695 CIF including 3D, 2D and 1D SiO2 models)

Not exhaustive list, run again GRINSP and you will find more...

References for these predictions :

1- Inorganic structure prediction with GRINSP. A. Le Bail, J. Appl. Cryst. 38 (2005) 389-395.
2- Predicted corner-sharing titanium silicates. A. Le Bail, Z. Kristallogr., Suppl. 26 (2007) 203-208.
3- Powerpoint file : Contribution to the "Gordon Conference Style" Workshop : Global Optimisation Techniques Applied to the Prediction of Structures, 5-7 July 2006, University College London (.ppt or zipped)
4- Advances in structure prediction of inorganic compounds. A. Le Bail, Report of 2nd Algerian Crystallography Congress, Algérie (2005).
5- Hypothetical AlF3 crystal structures, A. Le Bail, F. Calvayrac, J. Solid State Chem., 179 (2006) 3159-3166.
6- Inorganic structure prediction: too much and not enough, A. Le Bail, Solid State Phenomena 130 (2007) 1-6.
7- Frontiers between crystal structure prediction and determination by powder diffractometry, A. Le Bail, Powder Diffraction, S23 (2008) S5-S12.
8- Databases of virtual inorganic crystal structures and their applications, A. Le Bail, Phys. Chem. Chem. Phys. 12 (2010) 8521-8530. DOI: 10.1039/c003907c
Etc - search by yourself after all...

BUT... Many of these predictions will never be confirmed, guys are working hard on screening out unfeasible hypothetical zeolites :

a- Screening out unfeasible hypothetical zeolite structures via the closest non-adjacent O...O pair - Junran Lu, Lin Li, Hongxiao Cao, Yi Li and Jihong Yu -  Phys. Chem. Chem. Phys., 2017, 19, 1276-1280. DOI: 10.1039/c6cp06217b
b- Predicting New Zeolites: A Combination of Thermodynamic and Kinetic Factors - Ekaterina D. Kuznetsova,, Olga A. Blatova, and Vladislav A. Blatov -  Chem. Mater. 2018 - DOI:10.1021/acs.chemmater.8b00905

PCOD2130001   FD = 7.59   CIF

That model was proposed by GRINSP when trying to solve the structure of ITQ-37 in 2007 - but as shown later, ITQ-37 presents an interrupted 4-connected net, so that it was impossible to obtain it by using GRINSP...

PCOD3101110  FD = 9.48   CIF

PCOD3101817   FD = 10.19   CIF

PCOD3101685   FD = 10.23   CIF

PCOD3001605   FD  =  10.54   CIF

PCOD3000006   FD  =  10.61   CIF

PCOD3011029   FD  =  10.82   CIF

PCOD3002292   FD  =  11.24   CIF

PCOD3007568   FD  =  11.45   CIF

PCOD3002306   FD  =  11.56   CIF

PCOD3000975   FD  =  11.57   CIF

PCOD3002460   FD  =  11.72   CIF

PCOD3006638   FD  =  12.03   CIF

PCOD3007208   FD  =  13.30   CIF

PCOD3010970   FD = 16.59   CIF