Ultrathin\nBPH Nanosheets with Exceptional Water Adsorption\nProperties

The\nsynthesis of ultrathin BPH zeolite nanosheets from\nan aluminosilicate\ncolloidal suspension using exclusively inorganic structure directing\nagents under mild conditions is reported. The improved synthesis yields\nnanosheets of 4–7 nm and a Si/Al ratio of 1.5; combined 3D\nelectron diffraction and DFT calculations reveal the spatial distribution\nof extra-framework cations throughout the microporous structure. The\nultrathin BPH nanosheets exhibit high and regular intersheet mesoporosity,\nand substantially improved thermal stability. The notable mesoporosity\nbestows exceptional water adsorption behavior typically unseen for\nzeolites; the as-prepared material consists of up to 49% adsorbed\nH<sub>2</sub>O by weight and adsorbs up to 32 wt % H<sub>2</sub>O\nat 90% relative humidity. <sup>2</sup>H MAS NMR spectroscopy identifies\ndifferent types of O<sup>2</sup>H environments ascribed to silanol\nspecies exhibiting two motion behaviors. H<sub>2</sub>O sorption analysis\ndemonstrates reproducible behavior over multiple cycles and low temperature\nregeneration, making the ultrathin BPH nanosheets attractive candidates\nfor gas drying and membrane applications.