Christopher Powell was filmed by the group and the incident was streamed live on Facebook in a street in Holbeck, Leeds.
A court heard Powell, 51, believed he had been about to meet a teenager after making arrangements through the social networking app Grindr.
Bus driver Powell had instead made contact with a fake profile set up by the group Predator Exposure.
Christopher Dunn, prosecuting, said Powell had described how he wanted to perform sex acts on the teenager and sent sexually explicit photographs to the profile.
Mr Dunn said Powell made arrangements to meet up with the youngster on June 30 but was instead confronted by members of the group.
Two men detained Powell while filming the incident and police were called.
Powell was taken to Elland Road police station when officers arrived.
His car was searched and sex toys were found in the spare wheel compartment of his car.
Powell, of Meadowfields Drive, Crofton, Wakefield, pleaded guilty to attempting to cause or incite a child to engage in sexual activity, causing a child to watch sexual activity and attempting to meet a child following sexual grooming.
He was jailed for 32 months.
Christopher Morton, mitigating, said Powell was a married father of two and been sacked from his job with First bus company over his offending.
Mr Morton handed the court references written on behalf of Powell describing his work for the community as a school governor and for charity.
He added: "It is a sad case for a man who has lost virtually everything."
Mr Morton said Powell had been frank with his wife of 28 years and two adult children about his offending and continued to have the support of his family.
Jailing Powell, judge Geoffrey Marson, QC, said: "I am prepared to accept that this indeed is a tragic case. There is much to be said in your favour.
"People speak highly of your work as a school governor, indeed as a chair of governor."
Describing the offending, the judge said: "There can be no reason for travelling other than you had an intention to meet and carry out the sexual activity that you discussed."