Associate Professor CHUAH Gaik Khuan
B.Sc.(Hons), National University of Singapore, 1982; Ph.D., Texas A&M University, 1987.
Tel: (65)-6516-2839 |
Our main research area is on heterogeneous catalysis:
- Applications of zeolites in fine chemicals synthesis
- Green chemistry and catalysis
- Synthesis and applications of materials with tunable textural properties
- Photocatalysts in water remediation and synthesis
Zirconium phosphates are used as cation exchangers in the treatment of nuclear wastes and radioactive wastewater, acid catalysts and catalyst supports, intercalation host for drugs and other molecules, fast ion conductors and in chromatography. Zirconium phosphate exists in various crystal structures. In the α-form, Zr(HPO4)2·H2O, planes of zirconium atoms are bridged by phosphate groups which are alternately located above and below the planes. Unlike α-ZrP, γ-ZrP (Zr(PO4)(H2PO4)·2H2O)does not contain any HPO4− groups but rather, phosphates (PO43-) and dihydrogen phosphates (H2PO4−). The ion-exchange property arises from the protons, which are exchangeable. Because of the larger interlayer space, γ-ZrP can sorb larger ions than α-ZrP. However, synthesis methodologies to form crystalline zirconium phosphates typically involve the use of excess reagents, long reflux times or hydrothermal conditions. We have developed a minimalistic sustainable route using only zirconium oxychloride and phosphoric acid or sodium dihydrogen phosphate to form highly crystalline α- and γ-ZrP within hours (Fig. 1). Key features of this minimal solvent synthesis are the excellent yields obtained with high atom economy under mild conditions and ease of scalability. The crystalline γ-ZrP has extremely high selectivity to cesium even in the presence of 1000- or 500-fold excess Na+ or Ca2+, respectively. The removal efficiency was > 98% in the pH range of 2−5.5. As an ion exchanger for purification of dialysate, crystalline γ-ZrP shows higher uptake of ammonium and potassium ions than the amorphous gel compound currently used in sorbent cartridges. This sustainable protocol opens up opportunities for many practical applications of crystalline zirconium phosphates.
- CM3253 Materials Chemistry 1
- Cheng, Y.; Zhang, H.; Jaenicke, J. A.; Tan, C. P. E.; Chuah, G. K., Minimalistic Synthesis of α-Zirconium Diammonium Phosphate and Zirconia for Applications in Ion Exchange and Catalysis. ACS Sustainable Chem. Eng. 2019, 7, 895–904.
- Zhang, H.; Yang, W.; Roslan, I. I.; Jaenicke, S.; Chuah, G. K., A combo Zr-HY and Al-HY zeolite catalysts for the one-pot cascade transformation of biomass-derived furfural to γ-valerolactone. J. Catal. 2019, 375, 56–67.
- Roslan, I. I.; Ng, K. H.; Jaenicke, S.; Chuah, G. K., Photocatalytic regeneration of brominating agent in the visible light-mediated synthesis of imidazo[1,2-a]pyridines. Catal. Sci. Technol. 2019, 9, 1528–1534.
- Cheng, Y.; Wang, X.; Jaenicke, S.; Chuah, G. K., Mechanochemistry-based bynthesis of highly crystalline γ‑zirconium phosphate for selective ion exchange. Inorg. Chem. 2018, 57, 4370−4378.
- Zhang, H.; Han, A.; Okumura, K; Zhong, L.; Li, S.; Jaenicke, S.; Chuah, G. K., Selective hydrogenation of phenol to cyclohexanone by SiO2-supported rhodium nanoparticles under mild conditions. J. Catal. 2018, 364, 354–365.
- Roslan, I. I.; Ng, K. H.; Gondal, M. A.; Basheer, C.; Dastageer, M. A.; Jaenicke, S.; Chuah, G. K., Visible Light-Mediated Coupling of Thioureas and 1,3-Dicarbonyls: Towards a Leaving Group-Free Synthesis of Aminothiazoles. Adv. Synth. Catal. 2018, 360, 1584 – 1589.
- Han, A.; Zhang, H.; Chuah, G. K.; Jaenicke, S. Influence of the halide and exposed facets on the visible-light photoactivity of bismuth oxyhalides for selective aerobic oxidation of primary amines. Appl. Catal. B 2017, 219, 269–275.
- Cheng, Y.; Wang, X.; Jaenicke, S.; Chuah, G. K., Minimalistic Liquid-Assisted Route to Highly Crystalline α-Zirconium Phosphate. ChemSusChem 2017, 10, 3235-3242.
- Wang, J.; Okumura, K.; Jaenicke, S.; Chuah, G. K., Post-synthesized zirconium-containing Beta zeolite in Meerwein-Ponndorf-Verley reduction: Pros and cons. Appl. Catal. A-Gen. 2015, 493, 112-120.
- Fan, A.; Jaenicke, S.; Chuah, G. K., A heterogeneous Pd-Bi/C catalyst in the synthesis of L-lyxose and L-ribose from naturally occurring D-sugars. Org. Biomol. Chem. 2011, 9 (22), 7720-7726. [Hot paper].