Article pubs.acs.org/IECR
Smart Adsorbents Functionalized with Thermoresponsive Polymers for Selective Adsorption and Energy-Saving Regeneration Jia-Jia Ding, Jing Zhu, Yu-Xia Li, Xiao-Qin Liu, and Lin-Bing Sun* Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing 210009, China S Supporting Information *
ABSTRACT: Selective adsorption and energy-saving regeneration are two important issues for adsorptive separation. However, it is impossible for traditional adsorbents with changeless pore properties to realize both of them. In this study, a strategy was proposed to design and fabricate a new generation of adsorbents via grafting the thermoresponsive polymers (TPs), namely, poly(N-isopropylacrymide) (PNIPAM), onto the pore surface of mesoporous silica SBA-15. The TPs disperse homogeneously in pore space and act as molecular switches which are reversibly closed or opened with the change of temperature. At the temperature of adsorption below the lower critical solution temperature (LCST), TPs are extended as a result of their extensive hydrogen bonding interactions with water and the molecular switches are closed. It is easier for smaller adsorbates to enter than larger ones, and the selective adsorption can be consequently realized. At the temperature of desorption (above LCST), TPs shrink owing to their hydrogen bonding between polymer molecules and promote desorption of adsorbates owing to the opened molecular switches. The smart adsorbent can thus realize selective adsorption and energysaving desorption responsive to adsorption/desorption conditions by tunable pore properties. This is impossible for traditional adsorbents with changeless pores, although selective adsorption and energy-saving regeneration are extremely desired for adsorptive separation.
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INTRODUCTION In the chemical industry, separation always plays an important role. According to the second law of thermodynamics,1 separation can never be a spontaneous process and traditional techniques are usually somewhat expensive and energyconsuming.2,3 Distillation is commonly applied in the chemical industry, while the energy consumption is more than half of the total production energy and part of the energy can be saved with appropriate approaches.4,5 With a view to its cheap equipment,6 simple operation,7 and low energy consumption,8 adsorption is one of the most promising approaches to take the place of the traditional separation processes like distillation.9,10 Over the past decades, much work has been attempted to broaden the application of suitable adsorbents.11,12 Recent developments in ordered microporous and mesoporous materials represent a prominent advance in materials for adsorption.13,14 Microporous materials with small pores (
