Synthesis of Flower-Shaped Particles Composed of Phenylboronic Acid-Functionalized Microporous Organic Network Nanopetals for Efficient Enrichment of Salvianolic Acid B

Abstract

Selective enrichment and isolation of polar phenolic acid compounds from the complex matrix of traditional Chinese medicine Salvia miltiorrhiza (Danshen) is challenging yet highly desirable due to their excellent pharmacological activities on cardiovascular and cerebrovascular systems. However, owing to their polar and ionic characteristics, trace levels of phenolic acid compounds, and the complexity of traditional Chinese medicine matrices, the selectivity and adsorption capacity of conventional separation media remain limited. Therefore, the rational design of efficient and selective extractants is crucial. In this study, a phenylboronic acid-functionalized microporous organic network (p-PBA-MON), with nanoscale porosity (1.2 nm) and a high surface area (437.6 m² g^–1), was synthesized and employed as an adsorbent for the selective and efficient enrichment of the phenolic acid compound salvianolic acid B (SAB) from Salvia miltiorrhiza. A monomer containing phenylboronic acid groups was chosen to construct p-PBA-MON, forming specific five- or six-membered cyclic esters with cis-diol groups in SAB and providing synergistic π–π and hydrogen bonding sites. This results in the selective adsorption of SAB with ultrafast adsorption kinetics (<20 min, C₀ = 50 mg L^–1) and high adsorption capacity (217.4 mg g^–1). The synthesized p-PBA-MON tolerates the influences of ionic strength and humic acid and can be reused at least five times without a decrease in adsorption capacity. This study introduces an efficient adsorbent for the selective enrichment and separation of polar SAB from complex traditional Chinese medicine samples. This advancement could significantly extend the application of MON in the extraction and purification of active substances from Chinese medicine and promote its development in the separation of complex samples.