Table 2. Catalytic Performance of Non-activated Catalysts (unless Specified Otherwise) in Catalyzing CO₂ Cycloaddition with ECH at 80 °C for 3.5 h under Ambient CO₂ Pressure and Solvent-less Conditions.

entry	catalyst	% conversiona	% yield	% selectivitya	TONb	TOF (h–1)b
1	None (use only TBABr)	53(±1)		96
2	Vm (without TBABr)	trace
3	Vt (without TBABr)	trace
4	Eu(NO3)3·6H2O	79	74	96	2960	846
5	IVm	80	77	97	3080	880
6	Vm	84	84	95	3360	960
7	Vmc	81	81	95	3240	926
8	Vm crystal	79	77	95	3080	880
9	VIm	81	79	97	3160	903
10	VIIm	81	81	97	3240	926
11	VIIIm	82	82	94	3280	937
12	It	76	74	95	2960	846
13	IIt	76	74	95	2960	846
14	IIIt	75	73	96	2920	834
15	IVt	77	74	95	2960	846
16	Vt	77	74	94	2960	846
17	Vtc	77	73	95	2920	834
18	VIt	79	77	95	3080	880
19	VIIt	78	77	95	3080	880

^aAveraged from triplicate results with ±1 to ±3 standard deviation (based on ¹H NMR results).

^bCalculated from % yield:

^cWith prior activation (soaking in MeOH overnight and then heating at 80 °C for 30 min under N₂).