Catalyst screening for the carbonation of EMS^a.

Entry	Metal salt	PTC	Yield (%)
1	KI	—	0
2	KI	Ethylene glycol	<5
3	KI	Triethylene glycol	10
4	KI	Tetraethylene glycol	52
5	KI	PEG-200	55
6	KI	PEG-400	79
7	KI	PEG-600	78
8	KI	PEG-800	78
9	KI	PEG-1000	74
10	KI	PEG-2000	74
11	KI	PEG-4000	78
12	NaI	PEG-400	65
13	CaI2	PEG-400	0
14	ZnI2	PEG-400	0
15	KBr	PEG-400	0

^aReaction conditions: reaction temperature: 120 °C; reaction time: 18 h; CO₂ pressure: 1.0 MPa; stirring speed: 400 rpm; catalyst loading: 5 mol%; PTC concentration: 5 mol%; EMS: 5.0 g.