Munir Mohammed, 37, enlisted the help of pharmacist Rowaida el-Hassan on SingleMuslim.com after volunteering for a lone wolf mission directed by a man he believed was an IS commander on Facebook.
Mohammed, a Sudanese asylum seeker who arrived in the back of a lorry in February 2014, was arrested in December 2016 at his home in Leopold Street, Derby.
Police found two of the three components for the explosive TATP, manuals on how to make explosives, mobile phone detonators and ricin, a deadly poison.
Both he and Hassan, 33, of Willesden Lane, northwest London, denied preparing terrorist acts between November 2015 and December 2016.
An Old Bailey jury on Monday found the pair guilty of the plot and Judge Michael Topolski QC remanded the pair in custody, warning therm they face jail when they are sentenced on 22 February.
Following the verdicts, he said: "Munir Mohammed, you have been convicted of planning a potentially devastating terrorist attack by creating an explosive device and deploying it somewhere in the UK, targeting those you regarded as enemies of the Islamic State.
"Rowaida El-Hassan, you share the extremist mindset with Munir Mohammed and you were ideologically motivated to provide him with support, motivation and assistance.
"You knew he was engaging and planning an attack. You knew he was planning an explosion to kill and maim innocent people in the cause of Islamic State."
Mohammed, who was living in Derby, used Facebook to get in touch with an IS commander, asking him for a bomb-making recipe and further instructions.
He had also researched the deadly poison ricin while working illegally in a Kerry Foods factory making sauces for supermarket chains.
Hassan, a former Boots pharmacist, "rapidly formed an emotional attachment" after meeting Mohammed online, prosecutors said.
He sent her gory videos of IS executions, including some carried out by children.
She asked him to "send more" and helped guide him to the right chemicals for his bomb.
He bought two of the three ingredients required to make the explosive called triacetone triperoxide (TATP), known as Mother of Satan, and thought he had a third.
Investigators believe that it was only his lack of English that meant he had accidentally bought the wrong third ingredient.
He needed Hassan's help because hydrogen peroxide, one of the bomb's components is a "p-line" product, which means that customers have to speak to the pharmacist before it can be purchased.
But evidence suggested that Hassan was also discussing targets, at one point searching for: "Why is UK not fearful of attacks like Germany and France."
Anne Whyte QC, prosecuting, told the jury at the Old Bailey: "Rowaida Hassan was the educated assistant with a rallying cry when he needed it and the pharmaceutical knowledge to help.
"Munir Mohammed was the active heavy lifter. They were both assets to ISIS in their different ways."
DCI Paul Greenwood of the North-East Counter-Terrorism Unit, said: "We consider that Mohammed was in the later stages of a plot. He had bought the chemicals and although he had not had the tasking, there was a high risk that he could have launched an attack by Christmas."
Ms Whyte said: "This is a case which reflects the age in which we live. It demonstrates the relative ease with which acts of terrorism can be prepared, thanks to the internet.
"The prosecution allege that Munir Mohammed had resolved upon a lone wolf attack and that Rowaida el-Hassan was aware of his engagement with such a plan."
The jury was told that Mohammed was in contact over Facebook with an IS commander, who used the online identity Abubakr Kurdi.
"Kurdi was the one to give instructions and Mohammed was to carry them out", prosecutors said.
At one point, Rowaida el-Hassan messaged Munir Mohammed: "Oh you who believe! Fight those of the disbelievers who are close to you and let them find harshness in you.
"Perform jihad in Allah's cause for jihad is a tremendous door leading to paradise, through it Allah saves one from sadness and grief."
Mohammed accessed a video on how to make a crude version of ricin, titled: "Jihadi ideas for Lonely Lions."
In the space of three months Mohammed also downloaded three separate videos which showed how to make a bomb.
He had an IS video which showed how to make TATP, a YouTube video showing how to make TATP into a plastic explosive and an Arabic video which showed how to make a shaped charge.
