The phrase "accept as pledge" is correct and usable in written English.
It can be used in contexts where someone is agreeing to take something as a form of security or assurance, often in financial or legal situations.
Example: "The bank will accept as pledge the property title until the loan is fully repaid."
Alternatives: "accept as collateral" or "take as security."
The Sanders campaign did not accept her pledge as sufficiently detailed then, and candidate Sanders refused to do so again on Thursday.
That would tend to suggest that some kind of assessment is being made at a leadership level as to whether or not the Islamic State can feasibly accept a pledge of allegiance.
Isis subsequently accepted that pledge, though it came from two individuals who had no previous contact with the group, and thus accepted responsibility – as well as credit among supporters of Islamic militancy – for the attack.
But on Thursday, a Canadian federal court ruled against Mr. Lai, calling him a "common criminal" and saying it largely accepted as "strict, clear and unequivocal" China's pledges that it would not torture or execute him.
Mr. Giuliani went to the Stadium to accept the pledge.
And here's the hedge: Even if the stock falls and is worth only $50,000, Derivium will accept the pledged shares as full payment.
On security, he pledged to open negotiations with the Taliban, and this approach is now widely accepted as a necessary aspect of a comprehensive political solution to the conflict.
They were able to force President Obama's budget director Peter Orszag to write them a letter pledging to accept "pay-as-you-go budgeting" for everything other than "non-emergency spending" as the price for voting for the stimulus bill.
The difference when Kickstarter launches a local presence is that those posting projects can accept pledges in local currencies — although those pledging, as before, can come from anywhere.
IS accepted the pledge, naming the territory under Boko Haram's control as the Islamic State of West Africa Province and as being part of the global caliphate it was trying to establish.
