networksAll the reagents, including Zinc nitrate (Zn(NO3)2·6H2O), sil-ver nitrate (AgNO3), 28 wt.% aqueous ammonia, sodium carbonate(Na2CO3) and alcohol were analytical grade and without furtherpurification. Distilled water contained small amounts of chloridion(Cl−) was used in all experiments.In a typical procedure, a certain volume of 0.168 M AgNO3solu-tion and 150 mL of 0.1 M Zn(NO3)2solution were added into a flask.Then 7.5 mL aqueous ammonia (28 wt.%) was added into the flaskunder vigorous stirring, then the mixture was heated to 60◦C undermoderate stirring for 30 min, 22.5 mL of 1 M Na2CO3was droppedinto the flask within 15 min, then this reaction was maintainedfor 4 h. After cooling to room temperature, the precipitates wereseparated from the solution by centrifugation. Then the productswere washed with deionized water and ethanol two times respec-tively, and dried in the air at 60◦C for 24 h. Finally the precursorswere calcined at 200◦C in air for 30 min, then increased to 350◦Cmaintained for 4 h.