Synthesis of periodic mesoporous phosphorus–nitrogen frameworks by nanocasting from mesoporous silica using melt-infiltration

Abstract

Periodic mesoporous phosphorus–nitrogen (P–N) frameworks with p6mm hexagonal and Imm body centered cubic symmetries were synthesized by a solvent-free nanocasting route using periodic mesoporous silicas (SBA-15 and SBA-16) as hard templates and (PNCl₂)₃ as precursor. The (PNCl₂)₃ was molten at 120 °C in nitrogen atmosphere and infiltrated into the pores of mesoporous silicas. The nitridization of (PNCl₂)₃ in an ammonia atmosphere at 700 °C followed by the SiO₂ template removal by etching with a HF/acetone mixture resulted in the formation of the desired periodic mesoporous P–N frameworks with high surface areas of 240 to 380 m²·g⁻¹ and pore volumes in the range of 0.29 to 0.53 cm³·g⁻¹. The excellent mesopore uniformity and periodicity of the obtained specimens were studied by electron microscopy, small angle X-ray diffraction, N₂ sorption, FT-IR, EDS, and elemental analysis. The materials are thermally stable up to 550 and 700 °C in an inert atmosphere depending on the pore systems and exhibit photoluminescence between 280 and 450 nm.