Would it be grounds for impeachment if Trump declares a national emergency over the Wall?

This is where things appear to be headed. Neither side is backing down, and we can’t go on much longer with the shutdown. Trump will do anything to avoid losing, and has suggested that he may declare a national emergency. He has the authority to declare a national emergency over anything he wants, but in this case, could it be considered an abuse of power, and would it therefore be grounds for impeachment? I have been reluctant to back impeachment, but I think in this case it would be necessary as a constitutional issue. Otherwise there is no restraint on the president. He would have absolute authority.