Sol-gel preparation of titanium (IV)-immobilized hierarchically porous organosilica hybrid monoliths

Highlights: • A metal immobilized hierarchically porous hybrid monolith was synthesized via sol-gel method. • The surface area of optimal monolith could reach to 1170 m²/g. • The monoliths exhibited high adsorption capacity for pyridoxal 5′-phosphate. • The monolith owned excellent enrichment performance of low-abundance phosphopeptides. -- Abstract: Hierarchically porous monoliths as a key feature of biological materials have been applied in enrichment and separation. In this work, a metal immobilized hierarchically porous organosilica hybrid monolith was synthesized by hydrolysis and condensation of tetraethoxysilane (TEOS) and diethoxyphosphorylethyl-triethoxysilane (DPTS) under alkaline environment. Phosphonate ester groups were firstly introduced by the employment of DPTS as functional monomer, and then acidified to phosphonic acids. The surface area of optimal monolith could reach to 1170 m²/g, which simultaneously contained micropores and mesopores (4 nm) obtained from nitrogen sorption measurement. Meanwhile, mercury intrusion porosimetry (MIP) further demonstrated that macropores (1–3 μm) existed in monoliths. Followed by chelating with titanium ion (Ti⁴⁺), the hierarchically porous organosilica hybrid monoliths could be applied as IMAC materials. This synthesized process was easy-operating and time-saving, and avoided the tedious and complex process of traditional Ti⁴⁺-IMAC materials. Furthermore, the Ti⁴⁺-IMAC monoliths exhibited high adsorption capacity for pyridoxal 5′-phosphate (82.6 mg/g). The 3282 unique phosphopeptides could be identified from 100 μg of HeLa digests after enrichment with the monolith, exhibiting excellent enrichment performance of low-abundance phosphopeptides.